diff --git a/test/built-ins/Temporal/Calendar/from/calendar-string-leap-second.js b/test/built-ins/Temporal/Calendar/from/calendar-string-leap-second.js
new file mode 100644
index 0000000000..88ec4b5ac8
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/from/calendar-string-leap-second.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.from
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.Calendar.from(arg);
+assert.sameValue(
+  result1.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = Temporal.Calendar.from(arg);
+assert.sameValue(
+  result2.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..e310aaeac9
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateAdd/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateadd
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.dateAdd(arg, new Temporal.Duration());
+TemporalHelpers.assertPlainDate(
+  result1,
+  1976, 11, "M11", 18,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.dateAdd(arg, new Temporal.Duration());
+TemporalHelpers.assertPlainDate(
+  result2,
+  1976, 11, "M11", 18,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateAdd/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dateAdd/leap-second.js
new file mode 100644
index 0000000000..c1bf52aa35
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateAdd/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateadd
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.dateAdd(arg, new Temporal.Duration());
+TemporalHelpers.assertPlainDate(
+  result1,
+  2016, 12, "M12", 31,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.dateAdd(arg, new Temporal.Duration());
+TemporalHelpers.assertPlainDate(
+  result2,
+  2016, 12, "M12", 31,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..ba6e4372f1
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateUntil/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,25 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateuntil
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.dateUntil(arg, new Temporal.PlainDate(1976, 11, 19));
+TemporalHelpers.assertDuration(result1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for calendar (first argument)");
+const result2 = instance.dateUntil(new Temporal.PlainDate(1976, 11, 19), arg);
+TemporalHelpers.assertDuration(result2, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for calendar (second argument)");
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result3 = instance.dateUntil(arg, new Temporal.PlainDate(1976, 11, 19));
+TemporalHelpers.assertDuration(result3, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for calendar (nested property, first argument)");
+const result4 = instance.dateUntil(new Temporal.PlainDate(1976, 11, 19), arg);
+TemporalHelpers.assertDuration(result4, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for calendar (nested property, second argument)");
diff --git a/test/built-ins/Temporal/Calendar/prototype/dateUntil/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dateUntil/leap-second.js
new file mode 100644
index 0000000000..f28efbb20a
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dateUntil/leap-second.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dateuntil
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+let result = instance.dateUntil(arg, new Temporal.PlainDate(2017, 1, 1));
+TemporalHelpers.assertDuration(result, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for PlainDate (first argument)");
+result = instance.dateUntil(new Temporal.PlainDate(2017, 1, 1), arg);
+TemporalHelpers.assertDuration(result, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, "leap second is a valid ISO string for PlainDate (second argument)");
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+result = instance.dateUntil(arg, new Temporal.PlainDate(2017, 1, 1));
+TemporalHelpers.assertDuration(result, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, "second: 60 is ignored in property bag for PlainDate (first argument)");
+result = instance.dateUntil(new Temporal.PlainDate(2017, 1, 1), arg);
+TemporalHelpers.assertDuration(result, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, "second: 60 is ignored in property bag for PlainDate (second argument)");
diff --git a/test/built-ins/Temporal/Calendar/prototype/day/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/day/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..2bf759b8a5
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/day/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.day
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.day(arg);
+assert.sameValue(
+  result1,
+  18,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.day(arg);
+assert.sameValue(
+  result2,
+  18,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/day/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/day/leap-second.js
new file mode 100644
index 0000000000..38c3e724ea
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/day/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.day
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.day(arg);
+assert.sameValue(
+  result1,
+  31,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.day(arg);
+assert.sameValue(
+  result2,
+  31,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..fcd0ca2d74
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofweek
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.dayOfWeek(arg);
+assert.sameValue(
+  result1,
+  4,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.dayOfWeek(arg);
+assert.sameValue(
+  result2,
+  4,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/leap-second.js
new file mode 100644
index 0000000000..4d78c15bbc
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfWeek/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofweek
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.dayOfWeek(arg);
+assert.sameValue(
+  result1,
+  6,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.dayOfWeek(arg);
+assert.sameValue(
+  result2,
+  6,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..d51b2c0dcb
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofyear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.dayOfYear(arg);
+assert.sameValue(
+  result1,
+  323,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.dayOfYear(arg);
+assert.sameValue(
+  result2,
+  323,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/dayOfYear/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/leap-second.js
new file mode 100644
index 0000000000..f41dfb5f73
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/dayOfYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.dayofyear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.dayOfYear(arg);
+assert.sameValue(
+  result1,
+  366,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.dayOfYear(arg);
+assert.sameValue(
+  result2,
+  366,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..763ae9c73d
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinmonth
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.daysInMonth(arg);
+assert.sameValue(
+  result1,
+  30,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.daysInMonth(arg);
+assert.sameValue(
+  result2,
+  30,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInMonth/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/leap-second.js
new file mode 100644
index 0000000000..3274f44916
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInMonth/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinmonth
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.daysInMonth(arg);
+assert.sameValue(
+  result1,
+  31,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.daysInMonth(arg);
+assert.sameValue(
+  result2,
+  31,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..4d6d407a78
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinweek
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.daysInWeek(arg);
+assert.sameValue(
+  result1,
+  7,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.daysInWeek(arg);
+assert.sameValue(
+  result2,
+  7,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInWeek/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/leap-second.js
new file mode 100644
index 0000000000..b88af835e5
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInWeek/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinweek
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.daysInWeek(arg);
+assert.sameValue(
+  result1,
+  7,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.daysInWeek(arg);
+assert.sameValue(
+  result2,
+  7,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..027cf9da24
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinyear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.daysInYear(arg);
+assert.sameValue(
+  result1,
+  366,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.daysInYear(arg);
+assert.sameValue(
+  result2,
+  366,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/daysInYear/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/daysInYear/leap-second.js
new file mode 100644
index 0000000000..ab2f0fb25b
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/daysInYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.daysinyear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.daysInYear(arg);
+assert.sameValue(
+  result1,
+  366,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.daysInYear(arg);
+assert.sameValue(
+  result2,
+  366,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..a776948093
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.inleapyear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.inLeapYear(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.inLeapYear(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/inLeapYear/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/leap-second.js
new file mode 100644
index 0000000000..e64bef3048
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/inLeapYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.inleapyear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.inLeapYear(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.inLeapYear(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/month/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/month/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..313b31f512
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/month/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.month
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.month(arg);
+assert.sameValue(
+  result1,
+  11,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.month(arg);
+assert.sameValue(
+  result2,
+  11,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/month/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/month/leap-second.js
new file mode 100644
index 0000000000..61198fe9f4
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/month/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.month
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.month(arg);
+assert.sameValue(
+  result1,
+  12,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.month(arg);
+assert.sameValue(
+  result2,
+  12,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..7c8eb3e6cf
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthCode/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthcode
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.monthCode(arg);
+assert.sameValue(
+  result1,
+  "M11",
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.monthCode(arg);
+assert.sameValue(
+  result2,
+  "M11",
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthCode/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/monthCode/leap-second.js
new file mode 100644
index 0000000000..69c34c942b
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthCode/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthcode
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.monthCode(arg);
+assert.sameValue(
+  result1,
+  "M12",
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.monthCode(arg);
+assert.sameValue(
+  result2,
+  "M12",
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..001b3cde21
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthsinyear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.monthsInYear(arg);
+assert.sameValue(
+  result1,
+  12,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.monthsInYear(arg);
+assert.sameValue(
+  result2,
+  12,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/monthsInYear/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/leap-second.js
new file mode 100644
index 0000000000..7a80b2990e
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/monthsInYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.monthsinyear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.monthsInYear(arg);
+assert.sameValue(
+  result1,
+  12,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.monthsInYear(arg);
+assert.sameValue(
+  result2,
+  12,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..ba100b2b8c
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.weekofyear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.weekOfYear(arg);
+assert.sameValue(
+  result1,
+  47,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.weekOfYear(arg);
+assert.sameValue(
+  result2,
+  47,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/weekOfYear/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/leap-second.js
new file mode 100644
index 0000000000..6d9e969524
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/weekOfYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.weekofyear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.weekOfYear(arg);
+assert.sameValue(
+  result1,
+  52,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.weekOfYear(arg);
+assert.sameValue(
+  result2,
+  52,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/year/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/Calendar/prototype/year/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..d821211c53
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/year/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.year
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.year(arg);
+assert.sameValue(
+  result1,
+  1976,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.year(arg);
+assert.sameValue(
+  result2,
+  1976,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Calendar/prototype/year/leap-second.js b/test/built-ins/Temporal/Calendar/prototype/year/leap-second.js
new file mode 100644
index 0000000000..7520460ded
--- /dev/null
+++ b/test/built-ins/Temporal/Calendar/prototype/year/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.year
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.year(arg);
+assert.sameValue(
+  result1,
+  2016,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.year(arg);
+assert.sameValue(
+  result2,
+  2016,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/Duration/compare/timezone-string-leap-second.js b/test/built-ins/Temporal/Duration/compare/timezone-string-leap-second.js
new file mode 100644
index 0000000000..02368982a3
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/compare/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.compare
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Duration.compare(new Temporal.Duration(), new Temporal.Duration(), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } });
+Temporal.Duration.compare(new Temporal.Duration(), new Temporal.Duration(), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Duration.compare(new Temporal.Duration(), new Temporal.Duration(), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Duration.compare(new Temporal.Duration(), new Temporal.Duration(), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Duration/prototype/add/relativeto-leap-second.js b/test/built-ins/Temporal/Duration/prototype/add/relativeto-leap-second.js
new file mode 100644
index 0000000000..8e392f0e9c
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/relativeto-leap-second.js
@@ -0,0 +1,43 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.add
+description: Leap second is constrained in both an ISO string and a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1, 0, 0, 1);
+
+let relativeTo = "2016-12-31T23:59:60";
+const result1 = instance.add(new Temporal.Duration(0, 0, 0, 0, -24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result1,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDate relativeTo"
+);
+
+relativeTo = "2016-12-31T23:59:60+00:00[UTC]";
+const result2 = instance.add(new Temporal.Duration(0, 0, 0, 0, -24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result2,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for ZonedDateTime relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result3 = instance.add(new Temporal.Duration(0, 0, 0, 0, -24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result3,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for PlainDate relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60, timeZone: "UTC" };
+const result4 = instance.add(new Temporal.Duration(0, 0, 0, 0, -24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result4,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for ZonedDateTime relativeTo"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/add/timezone-string-leap-second.js b/test/built-ins/Temporal/Duration/prototype/add/timezone-string-leap-second.js
new file mode 100644
index 0000000000..a08b0dc14f
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/add/timezone-string-leap-second.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.add
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+instance.add(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } });
+instance.add(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.add(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.add(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Duration/prototype/round/relativeto-leap-second.js b/test/built-ins/Temporal/Duration/prototype/round/relativeto-leap-second.js
new file mode 100644
index 0000000000..7516624cc3
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/relativeto-leap-second.js
@@ -0,0 +1,43 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Leap second is constrained in both an ISO string and a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1, 0, 0, 0, 24);
+
+let relativeTo = "2016-12-31T23:59:60";
+const result1 = instance.round({ largestUnit: "years", relativeTo });
+TemporalHelpers.assertDuration(
+  result1,
+  1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDate relativeTo"
+);
+
+relativeTo = "2016-12-31T23:59:60+00:00[UTC]";
+const result2 = instance.round({ largestUnit: "years", relativeTo });
+TemporalHelpers.assertDuration(
+  result2,
+  1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for ZonedDateTime relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result3 = instance.round({ largestUnit: "years", relativeTo });
+TemporalHelpers.assertDuration(
+  result3,
+  1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for PlainDate relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60, timeZone: "UTC" };
+const result4 = instance.round({ largestUnit: "years", relativeTo });
+TemporalHelpers.assertDuration(
+  result4,
+  1, 0, 0, 1, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for ZonedDateTime relativeTo"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/round/timezone-string-leap-second.js b/test/built-ins/Temporal/Duration/prototype/round/timezone-string-leap-second.js
new file mode 100644
index 0000000000..73e01540e2
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/round/timezone-string-leap-second.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.round
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+instance.round({ largestUnit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone } });
+instance.round({ largestUnit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.round({ largestUnit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone } }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.round({ largestUnit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-leap-second.js b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-leap-second.js
new file mode 100644
index 0000000000..c9af63b33b
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/relativeto-leap-second.js
@@ -0,0 +1,43 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.subtract
+description: Leap second is constrained in both an ISO string and a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1, 0, 0, 1);
+
+let relativeTo = "2016-12-31T23:59:60";
+const result1 = instance.subtract(new Temporal.Duration(0, 0, 0, 0, 24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result1,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDate relativeTo"
+);
+
+relativeTo = "2016-12-31T23:59:60+00:00[UTC]";
+const result2 = instance.subtract(new Temporal.Duration(0, 0, 0, 0, 24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result2,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for ZonedDateTime relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result3 = instance.subtract(new Temporal.Duration(0, 0, 0, 0, 24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result3,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for PlainDate relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60, timeZone: "UTC" };
+const result4 = instance.subtract(new Temporal.Duration(0, 0, 0, 0, 24), { relativeTo });
+TemporalHelpers.assertDuration(
+  result4,
+  1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is valid in a property bag for ZonedDateTime relativeTo"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/subtract/timezone-string-leap-second.js b/test/built-ins/Temporal/Duration/prototype/subtract/timezone-string-leap-second.js
new file mode 100644
index 0000000000..5cd39edc24
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/subtract/timezone-string-leap-second.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.subtract
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+instance.subtract(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } });
+instance.subtract(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.subtract(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone } }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.subtract(new Temporal.Duration(1), { relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Duration/prototype/total/relativeto-leap-second.js b/test/built-ins/Temporal/Duration/prototype/total/relativeto-leap-second.js
new file mode 100644
index 0000000000..3602203fc2
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/total/relativeto-leap-second.js
@@ -0,0 +1,42 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.total
+description: Leap second is constrained in both an ISO string and a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1, 0, 0, 0, 24);
+
+let relativeTo = "2016-12-31T23:59:60";
+const result1 = instance.total({ unit: "days", relativeTo });
+assert.sameValue(
+  result1,
+  366,
+  "leap second is a valid ISO string for PlainDate relativeTo"
+);
+
+relativeTo = "2016-12-31T23:59:60+00:00[UTC]";
+const result2 = instance.total({ unit: "days", relativeTo });
+assert.sameValue(
+  result2,
+  366,
+  "leap second is a valid ISO string for ZonedDateTime relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result3 = instance.total({ unit: "days", relativeTo });
+assert.sameValue(
+  result3,
+  366,
+  "second: 60 is valid in a property bag for PlainDate relativeTo"
+);
+
+relativeTo = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60, timeZone: "UTC" };
+const result4 = instance.total({ unit: "days", relativeTo });
+assert.sameValue(
+  result4,
+  366,
+  "second: 60 is valid in a property bag for ZonedDateTime relativeTo"
+);
diff --git a/test/built-ins/Temporal/Duration/prototype/total/timezone-string-leap-second.js b/test/built-ins/Temporal/Duration/prototype/total/timezone-string-leap-second.js
new file mode 100644
index 0000000000..0167a3c6dd
--- /dev/null
+++ b/test/built-ins/Temporal/Duration/prototype/total/timezone-string-leap-second.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.duration.prototype.total
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Duration(1);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+instance.total({ unit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone } });
+instance.total({ unit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.total({ unit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone } }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.total({ unit: "months", relativeTo: { year: 2000, month: 5, day: 2, timeZone: { timeZone } } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Instant/compare/leap-second.js b/test/built-ins/Temporal/Instant/compare/leap-second.js
new file mode 100644
index 0000000000..b2f5967d92
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/compare/leap-second.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.compare
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const other = new Temporal.Instant(1_483_228_799_000_000_000n);
+const arg = "2016-12-31T23:59:60Z";
+const result1 = Temporal.Instant.compare(arg, other);
+assert.sameValue(result1, 0, "leap second is a valid ISO string for Instant (first argument)");
+const result2 = Temporal.Instant.compare(other, arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for Instant (second argument)");
diff --git a/test/built-ins/Temporal/Instant/from/leap-second.js b/test/built-ins/Temporal/Instant/from/leap-second.js
new file mode 100644
index 0000000000..379aa7b114
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/from/leap-second.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.from
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const arg = "2016-12-31T23:59:60Z";
+const result = Temporal.Instant.from(arg);
+assert.sameValue(
+  result.epochNanoseconds,
+  1_483_228_799_000_000_000n,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/Instant/prototype/equals/leap-second.js b/test/built-ins/Temporal/Instant/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..547cbcfe85
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/equals/leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.equals
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(1_483_228_799_000_000_000n);
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.equals(arg);
+assert.sameValue(
+  result,
+  true,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/Instant/prototype/since/leap-second.js b/test/built-ins/Temporal/Instant/prototype/since/leap-second.js
new file mode 100644
index 0000000000..298aeb99b9
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/since/leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.since
+description: Leap second is a valid ISO string for Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(1_483_228_799_000_000_000n);
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/Instant/prototype/toString/timezone-string-leap-second.js b/test/built-ins/Temporal/Instant/prototype/toString/timezone-string-leap-second.js
new file mode 100644
index 0000000000..72e3391394
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/toString/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tostring
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toString({ timeZone });
+assert.sameValue(result1.substr(-6), "+00:00", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toString({ timeZone: { timeZone } });
+assert.sameValue(result2.substr(-6), "+00:00", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toString({ timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toString({ timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/calendar-string-leap-second.js b/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/calendar-string-leap-second.js
new file mode 100644
index 0000000000..7264f33377
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/calendar-string-leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(1_000_000_000_000_000_000n);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.toZonedDateTime({ calendar: arg, timeZone: "UTC" });
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = instance.toZonedDateTime({ calendar: arg, timeZone: "UTC" });
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..b3a25f04a9
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/toZonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toZonedDateTime({ timeZone, calendar: "iso8601" });
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toZonedDateTime({ timeZone: { timeZone }, calendar: "iso8601" });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toZonedDateTime({ timeZone, calendar: "iso8601" }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toZonedDateTime({ timeZone: { timeZone }, calendar: "iso8601" }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/timezone-string-leap-second.js b/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/timezone-string-leap-second.js
new file mode 100644
index 0000000000..46be8be647
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.tozoneddatetimeiso
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(0n);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toZonedDateTimeISO(timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toZonedDateTimeISO({ timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toZonedDateTimeISO(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toZonedDateTimeISO({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Instant/prototype/until/leap-second.js b/test/built-ins/Temporal/Instant/prototype/until/leap-second.js
new file mode 100644
index 0000000000..5c19ac969a
--- /dev/null
+++ b/test/built-ins/Temporal/Instant/prototype/until/leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.instant.prototype.until
+description: Leap second is a valid ISO string for Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Instant(1_483_228_799_000_000_000n);
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/Now/plainDate/calendar-string-leap-second.js b/test/built-ins/Temporal/Now/plainDate/calendar-string-leap-second.js
new file mode 100644
index 0000000000..25c6a9bd3b
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDate/calendar-string-leap-second.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindate
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.Now.plainDate(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = Temporal.Now.plainDate(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Now/plainDate/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/plainDate/timezone-string-leap-second.js
new file mode 100644
index 0000000000..93db0e2f4c
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDate/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindate
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Now.plainDate("iso8601", timeZone);
+Temporal.Now.plainDate("iso8601", { timeZone });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.plainDate("iso8601", timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.plainDate("iso8601", { timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/plainDateISO/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/plainDateISO/timezone-string-leap-second.js
new file mode 100644
index 0000000000..54f01540c1
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDateISO/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindateiso
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Now.plainDateISO(timeZone);
+Temporal.Now.plainDateISO({ timeZone });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.plainDateISO(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.plainDateISO({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/plainDateTime/calendar-string-leap-second.js b/test/built-ins/Temporal/Now/plainDateTime/calendar-string-leap-second.js
new file mode 100644
index 0000000000..98af04f808
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDateTime/calendar-string-leap-second.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.Now.plainDateTime(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = Temporal.Now.plainDateTime(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Now/plainDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/plainDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..e080f9aa85
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDateTime/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Now.plainDateTime("iso8601", timeZone);
+Temporal.Now.plainDateTime("iso8601", { timeZone });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.plainDateTime("iso8601", timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.plainDateTime("iso8601", { timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-leap-second.js
new file mode 100644
index 0000000000..4fc82538c2
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainDateTimeISO/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaindatetimeiso
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Now.plainDateTimeISO(timeZone);
+Temporal.Now.plainDateTimeISO({ timeZone });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.plainDateTimeISO(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.plainDateTimeISO({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/plainTimeISO/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/plainTimeISO/timezone-string-leap-second.js
new file mode 100644
index 0000000000..f37d00c9b2
--- /dev/null
+++ b/test/built-ins/Temporal/Now/plainTimeISO/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.plaintimeiso
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// A string with a leap second is a valid ISO string, so the following two
+// operations should not throw
+
+Temporal.Now.plainTimeISO(timeZone);
+Temporal.Now.plainTimeISO({ timeZone });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.plainTimeISO(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.plainTimeISO({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/zonedDateTime/calendar-string-leap-second.js b/test/built-ins/Temporal/Now/zonedDateTime/calendar-string-leap-second.js
new file mode 100644
index 0000000000..dde4ad71fe
--- /dev/null
+++ b/test/built-ins/Temporal/Now/zonedDateTime/calendar-string-leap-second.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.zoneddatetime
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.Now.zonedDateTime(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = Temporal.Now.zonedDateTime(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/Now/zonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/zonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..b91fd58cdf
--- /dev/null
+++ b/test/built-ins/Temporal/Now/zonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.zoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = Temporal.Now.zonedDateTime("iso8601", timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = Temporal.Now.zonedDateTime("iso8601", { timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.zonedDateTime("iso8601", timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.zonedDateTime("iso8601", { timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/Now/zonedDateTimeISO/timezone-string-leap-second.js b/test/built-ins/Temporal/Now/zonedDateTimeISO/timezone-string-leap-second.js
new file mode 100644
index 0000000000..f5a1dbaf77
--- /dev/null
+++ b/test/built-ins/Temporal/Now/zonedDateTimeISO/timezone-string-leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.now.zoneddatetimeiso
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = Temporal.Now.zonedDateTimeISO(timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = Temporal.Now.zonedDateTimeISO({ timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.Now.zonedDateTimeISO(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.Now.zonedDateTimeISO({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..94b12a67ab
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,22 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.compare
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = Temporal.PlainDate.compare(arg, new Temporal.PlainDate(1976, 11, 18));
+assert.sameValue(result1, 0, "leap second is a valid ISO string for calendar (first argument)");
+const result2 = Temporal.PlainDate.compare(new Temporal.PlainDate(1976, 11, 18), arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for calendar (first argument)");
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result3 = Temporal.PlainDate.compare(arg, new Temporal.PlainDate(1976, 11, 18));
+assert.sameValue(result3, 0, "leap second is a valid ISO string for calendar (nested property, first argument)");
+const result4 = Temporal.PlainDate.compare(new Temporal.PlainDate(1976, 11, 18), arg);
+assert.sameValue(result4, 0, "leap second is a valid ISO string for calendar (nested property, second argument)");
diff --git a/test/built-ins/Temporal/PlainDate/compare/leap-second.js b/test/built-ins/Temporal/PlainDate/compare/leap-second.js
new file mode 100644
index 0000000000..125edba5a7
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/compare/leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.compare
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+let result = Temporal.PlainDate.compare(arg, new Temporal.PlainDate(2016, 12, 31));
+assert.sameValue(result, 0, "leap second is a valid ISO string for PlainDate (first argument)");
+result = Temporal.PlainDate.compare(new Temporal.PlainDate(2016, 12, 31), arg);
+assert.sameValue(result, 0, "leap second is a valid ISO string for PlainDate (second argument)");
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+result = Temporal.PlainDate.compare(arg, new Temporal.PlainDate(2016, 12, 31));
+assert.sameValue(result, 0, "second: 60 is ignored in property bag for PlainDate (first argument)");
+result = Temporal.PlainDate.compare(new Temporal.PlainDate(2016, 12, 31), arg);
+assert.sameValue(result, 0, "second: 60 is ignored in property bag for PlainDate (second argument)");
diff --git a/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..4455b5fc2f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.from
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = Temporal.PlainDate.from(arg);
+TemporalHelpers.assertPlainDate(
+  result1,
+  1976, 11, "M11", 18,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = Temporal.PlainDate.from(arg);
+TemporalHelpers.assertPlainDate(
+  result2,
+  1976, 11, "M11", 18,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDate/from/leap-second.js b/test/built-ins/Temporal/PlainDate/from/leap-second.js
new file mode 100644
index 0000000000..0b523cf539
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/from/leap-second.js
@@ -0,0 +1,41 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.from
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainDate.from(arg);
+TemporalHelpers.assertPlainDate(
+  result1,
+  2016, 12, "M12", 31,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+const result2 = Temporal.PlainDate.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainDate(
+  result2,
+  2016, 12, "M12", 31,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainDate.from(arg);
+TemporalHelpers.assertPlainDate(
+  result3,
+  2016, 12, "M12", 31,
+  "second: 60 is ignored in property bag for PlainDate"
+);
+
+const result4 = Temporal.PlainDate.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainDate(
+  result4,
+  2016, 12, "M12", 31,
+  "second: 60 is ignored in property bag for PlainDate even with overflow: reject"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..2d24e808b2
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.equals
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/equals/leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..56f946877a
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.equals
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2016, 12, 31);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..c65e3e141f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.since
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/since/leap-second.js
new file mode 100644
index 0000000000..f182e0582f
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.since
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2016, 12, 31);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/leap-second.js
new file mode 100644
index 0000000000..5b06e59dd1
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/toPlainDateTime/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.toplaindatetime
+description: Leap second is a valid ISO string for PlainTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  2000, 5, "M05", 2, 23, 59, 59, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  2000, 5, "M05", 2, 23, 59, 59, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/leap-second.js
new file mode 100644
index 0000000000..c8d07074fc
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for PlainTime
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.toZonedDateTime({ plainTime: arg, timeZone: "UTC" });
+assert.sameValue(
+  result1.epochNanoseconds,
+  957311999_000_000_000n,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.toZonedDateTime({ plainTime: arg, timeZone: "UTC" });
+assert.sameValue(
+  result2.epochNanoseconds,
+  957311999_000_000_000n,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..7265aca261
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/toZonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2000, 5, 2);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toZonedDateTime(timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toZonedDateTime({ timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toZonedDateTime(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toZonedDateTime({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..a0a12252cc
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.until
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/until/leap-second.js
new file mode 100644
index 0000000000..ba46445e78
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.until
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2016, 12, 31);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-string-leap-second.js b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-string-leap-second.js
new file mode 100644
index 0000000000..7bd95a80cd
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-string-leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.withcalendar
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(1976, 11, 18, { id: "replace-me" });
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withCalendar(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = instance.withCalendar(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..37547e3272
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.compare
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(1976, 11, 18));
+assert.sameValue(result1, 0, "leap second is a valid ISO string for calendar (first argument)");
+const result2 = Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(1976, 11, 18), arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for calendar (second argument)");
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result3 = Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(1976, 11, 18));
+assert.sameValue(result3, 0, "leap second is a valid ISO string for calendar (nested property, first argument)");
+const result4 = Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(1976, 11, 18), arg);
+assert.sameValue(result4, 0, "leap second is a valid ISO string for calendar (nested property, second argument)");
+
diff --git a/test/built-ins/Temporal/PlainDateTime/compare/leap-second.js b/test/built-ins/Temporal/PlainDateTime/compare/leap-second.js
new file mode 100644
index 0000000000..fde64d43a2
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/compare/leap-second.js
@@ -0,0 +1,21 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.compare
+description: Leap second is a valid ISO string for PlainDateTime
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59));
+assert.sameValue(result1, 0, "leap second is a valid ISO string for PlainDateTime (first argument)");
+const result2 = Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59), arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for PlainDateTime (second argument)");
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59));
+assert.sameValue(result3, 0, "second: 60 is constrained in property bag for PlainDateTime (first argument)");
+const result4 = Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59), arg);
+assert.sameValue(result4, 0, "second: 60 is constrained in property bag for PlainDateTime (second argument)");
diff --git a/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..4e19d8ac56
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.from
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = Temporal.PlainDateTime.from(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  1976, 11, "M11", 18, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = Temporal.PlainDateTime.from(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  1976, 11, "M11", 18, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/from/leap-second.js b/test/built-ins/Temporal/PlainDateTime/from/leap-second.js
index 41cfa3d1ff..9a1a78c1fe 100644
--- a/test/built-ins/Temporal/PlainDateTime/from/leap-second.js
+++ b/test/built-ins/Temporal/PlainDateTime/from/leap-second.js
@@ -3,33 +3,38 @@
 
 /*---
 esid: sec-temporal.plaindatetime.from
-description: Leap seconds may be accepted or rejected
-features: [Temporal]
+description: Leap second is a valid ISO string for PlainDateTime
 includes: [temporalHelpers.js]
+features: [Temporal]
 ---*/
 
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainDateTime.from(arg);
 TemporalHelpers.assertPlainDateTime(
-  Temporal.PlainDateTime.from("2016-12-31T23:59:60"),
+  result1,
   2016, 12, "M12", 31, 23, 59, 59, 0, 0, 0,
-  "ISO string with leap second is constrained"
+  "leap second is a valid ISO string for PlainDateTime"
 );
 
+const result2 = Temporal.PlainDateTime.from(arg);
 TemporalHelpers.assertPlainDateTime(
-  Temporal.PlainDateTime.from("2016-12-31T23:59:60", {overflow: "reject"}),
+  result2,
   2016, 12, "M12", 31, 23, 59, 59, 0, 0, 0,
-  "ISO string with leap second is constrained (overflow = reject)"
+  "leap second is a valid ISO string for PlainDateTime even with overflow: reject"
 );
 
-const leap = {year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60};
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
 
+const result3 = Temporal.PlainDateTime.from(arg);
 TemporalHelpers.assertPlainDateTime(
-  Temporal.PlainDateTime.from(leap),
+  result3,
   2016, 12, "M12", 31, 23, 59, 59, 0, 0, 0,
-  "constrain leap second"
+  "second: 60 is constrained in property bag for PlainDateTime"
 );
 
 assert.throws(
   RangeError,
-  () => Temporal.PlainDateTime.from(leap, {overflow: "reject"}),
-  "reject leap second (plain object argument)"
+  () => Temporal.PlainDateTime.from(arg, { overflow: "reject" }),
+  "second: 60 is rejected in property bag for PlainDateTime with overflow: reject"
 );
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..2ef93da20c
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.equals
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/equals/leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..f8687efb4d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.equals
+description: Leap second is a valid ISO string for PlainDateTime
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainDateTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainDateTime"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..dd989748cc
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/leap-second.js
new file mode 100644
index 0000000000..44a464e405
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.since
+description: Leap second is a valid ISO string for PlainDateTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDateTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainDateTime"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..9b02984eb9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toZonedDateTime(timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toZonedDateTime({ timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toZonedDateTime(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toZonedDateTime({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..b49bd1593d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/leap-second.js
new file mode 100644
index 0000000000..352899ac08
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.until
+description: Leap second is a valid ISO string for PlainDateTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2016, 12, 31, 23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainDateTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainDateTime"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-string-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-string-leap-second.js
new file mode 100644
index 0000000000..02ea408591
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-string-leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withcalendar
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456, 789, { id: "replace-me" });
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withCalendar(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = instance.withCalendar(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..db9a51215e
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.withPlainDate(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  1976, 11, "M11", 18, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.withPlainDate(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  1976, 11, "M11", 18, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/leap-second.js
new file mode 100644
index 0000000000..39c6186177
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainDate/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaindate
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withPlainDate(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  2016, 12, "M12", 31, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.withPlainDate(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  2016, 12, "M12", 31, 12, 34, 56, 987, 654, 321,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/leap-second.js b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/leap-second.js
new file mode 100644
index 0000000000..4cfd1e0ec3
--- /dev/null
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withPlainTime/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.withplaintime
+description: Leap second is a valid ISO string for PlainTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2000, 5, 2, 12, 34, 56, 987, 654, 321);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withPlainTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  2000, 5, "M05", 2, 23, 59, 59, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.withPlainTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  2000, 5, "M05", 2, 23, 59, 59, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..1a2d2cd042
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.from
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { monthCode: "M11", day: 18, calendar };
+const result1 = Temporal.PlainMonthDay.from(arg);
+TemporalHelpers.assertPlainMonthDay(
+  result1,
+  "M11", 18,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = Temporal.PlainMonthDay.from(arg);
+TemporalHelpers.assertPlainMonthDay(
+  result2,
+  "M11", 18,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/from/leap-second.js b/test/built-ins/Temporal/PlainMonthDay/from/leap-second.js
new file mode 100644
index 0000000000..450a2f832c
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/from/leap-second.js
@@ -0,0 +1,41 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.from
+description: Leap second is a valid ISO string for PlainMonthDay
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainMonthDay.from(arg);
+TemporalHelpers.assertPlainMonthDay(
+  result1,
+  "M12", 31,
+  "leap second is a valid ISO string for PlainMonthDay"
+);
+
+const result2 = Temporal.PlainMonthDay.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainMonthDay(
+  result2,
+  "M12", 31,
+  "leap second is a valid ISO string for PlainMonthDay"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainMonthDay.from(arg);
+TemporalHelpers.assertPlainMonthDay(
+  result3,
+  "M12", 31,
+  "second: 60 is ignored in property bag for PlainMonthDay"
+);
+
+const result4 = Temporal.PlainMonthDay.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainMonthDay(
+  result4,
+  "M12", 31,
+  "second: 60 is ignored in property bag for PlainMonthDay even with overflow: reject"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..202f5f4318
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.equals
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainMonthDay(11, 18);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { monthCode: "M11", day: 18, calendar };
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/leap-second.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..f950ce0f1d
--- /dev/null
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday.prototype.equals
+description: Leap second is a valid ISO string for PlainMonthDay
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainMonthDay(12, 31);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainMonthDay"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainMonthDay"
+);
diff --git a/test/built-ins/Temporal/PlainTime/compare/leap-second.js b/test/built-ins/Temporal/PlainTime/compare/leap-second.js
new file mode 100644
index 0000000000..186fed3a8e
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/compare/leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.compare
+description: Leap second is a valid ISO string for PlainTime
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+const result1 = Temporal.PlainTime.compare(arg, new Temporal.PlainTime(23, 59, 59));
+assert.sameValue(result1, 0, "leap second is a valid ISO string for PlainTime (first argument)");
+const result2 = Temporal.PlainTime.compare(new Temporal.PlainTime(23, 59, 59), arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for PlainTime (first argument)");
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result3 = Temporal.PlainTime.compare(arg, new Temporal.PlainTime(23, 59, 59));
+assert.sameValue(result3, 0, "second: 60 is ignored in property bag for PlainTime (first argument)");
+const result4 = Temporal.PlainTime.compare(new Temporal.PlainTime(23, 59, 59), arg);
+assert.sameValue(result4, 0, "second: 60 is ignored in property bag for PlainTime (second argument)");
diff --git a/test/built-ins/Temporal/PlainTime/from/leap-second.js b/test/built-ins/Temporal/PlainTime/from/leap-second.js
new file mode 100644
index 0000000000..5626c74666
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/from/leap-second.js
@@ -0,0 +1,40 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.from
+description: Leap second is a valid ISO string for PlainTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainTime.from(arg);
+TemporalHelpers.assertPlainTime(
+  result1,
+  23, 59, 59, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+const result2 = Temporal.PlainTime.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainTime(
+  result2,
+  23, 59, 59, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainTime.from(arg);
+TemporalHelpers.assertPlainTime(
+  result3,
+  23, 59, 59, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainTime"
+);
+
+assert.throws(
+  RangeError,
+  () => Temporal.PlainTime.from(arg, { overflow: "reject" }),
+  "second: 60 is rejected in property bag for PlainTime with overflow: reject"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/equals/leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..066a2cafec
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.equals
+description: Leap second is a valid ISO string for PlainTime
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/since/leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/since/leap-second.js
new file mode 100644
index 0000000000..7457e58233
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/since/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.since
+description: Leap second is a valid ISO string for PlainTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..6e38a93003
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.toplaindatetime
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  1976, 11, "M11", 18, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  1976, 11, "M11", 18, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/leap-second.js
new file mode 100644
index 0000000000..ea1ee61223
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toPlainDateTime/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.toplaindatetime
+description: Leap second is a valid ISO string for PlainDate
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result1,
+  2016, 12, "M12", 31, 12, 34, 56, 987, 654, 321,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.toPlainDateTime(arg);
+TemporalHelpers.assertPlainDateTime(
+  result2,
+  2016, 12, "M12", 31, 12, 34, 56, 987, 654, 321,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..975d536ff8
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.toZonedDateTime({ plainDate: arg, timeZone: "UTC" });
+assert.sameValue(
+  result1.epochNanoseconds,
+  217_168_496_987_654_321n,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.toZonedDateTime({ plainDate: arg, timeZone: "UTC" });
+assert.sameValue(
+  result2.epochNanoseconds,
+  217_168_496_987_654_321n,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/leap-second.js
new file mode 100644
index 0000000000..b882057429
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(12, 34, 56, 987, 654, 321);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.toZonedDateTime({ plainDate: arg, timeZone: "UTC" });
+assert.sameValue(
+  result1.epochNanoseconds,
+  1_483_187_696_987_654_321n,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.toZonedDateTime({ plainDate: arg, timeZone: "UTC" });
+assert.sameValue(
+  result2.epochNanoseconds,
+  1_483_187_696_987_654_321n,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..78dffeb2c9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/toZonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.tozoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime();
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.toZonedDateTime({ plainDate: new Temporal.PlainDate(2000, 5, 2), timeZone });
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.toZonedDateTime({ plainDate: new Temporal.PlainDate(2000, 5, 2), timeZone: { timeZone } });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.toZonedDateTime({ plainDate: new Temporal.PlainDate(2000, 5, 2), timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.toZonedDateTime({ plainDate: new Temporal.PlainDate(2000, 5, 2), timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/PlainTime/prototype/until/leap-second.js b/test/built-ins/Temporal/PlainTime/prototype/until/leap-second.js
new file mode 100644
index 0000000000..a19b99b4d9
--- /dev/null
+++ b/test/built-ins/Temporal/PlainTime/prototype/until/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaintime.prototype.until
+description: Leap second is a valid ISO string for PlainTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainTime(23, 59, 59);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/leap-second.js b/test/built-ins/Temporal/PlainYearMonth/compare/leap-second.js
new file mode 100644
index 0000000000..c3c755a4ef
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/leap-second.js
@@ -0,0 +1,22 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.compare
+description: Leap second is a valid ISO string for PlainYearMonth
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainYearMonth.compare(arg, new Temporal.PlainYearMonth(2016, 12));
+assert.sameValue(result1, 0, "leap second is a valid ISO string for PlainYearMonth (first argument)");
+const result2 = Temporal.PlainYearMonth.compare(new Temporal.PlainYearMonth(2016, 12), arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for PlainYearMonth (second argument)");
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainYearMonth.compare(arg, new Temporal.PlainYearMonth(2016, 12));
+assert.sameValue(result3, 0, "second: 60 is ignored in property bag for PlainYearMonth (first argument)");
+const result4 = Temporal.PlainYearMonth.compare(new Temporal.PlainYearMonth(2016, 12), arg);
+assert.sameValue(result4, 0, "second: 60 is ignored in property bag for PlainYearMonth (second argument)");
diff --git a/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..34160a40db
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.from
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 2019, monthCode: "M06", calendar };
+const result1 = Temporal.PlainYearMonth.from(arg);
+TemporalHelpers.assertPlainYearMonth(
+  result1,
+  2019, 6, "M06",
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 2019, monthCode: "M06", calendar: { calendar } };
+const result2 = Temporal.PlainYearMonth.from(arg);
+TemporalHelpers.assertPlainYearMonth(
+  result2,
+  2019, 6, "M06",
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/from/leap-second.js b/test/built-ins/Temporal/PlainYearMonth/from/leap-second.js
new file mode 100644
index 0000000000..818a43dc1b
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/from/leap-second.js
@@ -0,0 +1,41 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.from
+description: Leap second is a valid ISO string for PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60";
+
+const result1 = Temporal.PlainYearMonth.from(arg);
+TemporalHelpers.assertPlainYearMonth(
+  result1,
+  2016, 12, "M12",
+  "leap second is a valid ISO string for PlainYearMonth"
+);
+
+const result2 = Temporal.PlainYearMonth.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainYearMonth(
+  result2,
+  2016, 12, "M12",
+  "leap second is a valid ISO string for PlainYearMonth"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+
+const result3 = Temporal.PlainYearMonth.from(arg);
+TemporalHelpers.assertPlainYearMonth(
+  result3,
+  2016, 12, "M12",
+  "second: 60 is ignored in property bag for PlainYearMonth"
+);
+
+const result4 = Temporal.PlainYearMonth.from(arg, { overflow: "reject" });
+TemporalHelpers.assertPlainYearMonth(
+  result4,
+  2016, 12, "M12",
+  "second: 60 is ignored in property bag for PlainYearMonth even with overflow: reject"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..3d446c7789
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.equals
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2019, 6);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 2019, monthCode: "M06", calendar };
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 2019, monthCode: "M06", calendar: { calendar } };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..210c420957
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.equals
+description: Leap second is a valid ISO string for PlainYearMonth
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2016, 12);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for PlainYearMonth"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "second: 60 is ignored in property bag for PlainYearMonth"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..9a276a1a4c
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2019, 6);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 2019, monthCode: "M06", calendar };
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 2019, monthCode: "M06", calendar: { calendar } };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/leap-second.js
new file mode 100644
index 0000000000..651cf05d32
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.since
+description: Leap second is a valid ISO string for PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2016, 12);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainYearMonth"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainYearMonth"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..883d319460
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2019, 6);
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 2019, monthCode: "M06", calendar };
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 2019, monthCode: "M06", calendar: { calendar } };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/leap-second.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/leap-second.js
new file mode 100644
index 0000000000..3c82e66e15
--- /dev/null
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth.prototype.until
+description: Leap second is a valid ISO string for PlainYearMonth
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2016, 12);
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for PlainYearMonth"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "second: 60 is ignored in property bag for PlainYearMonth"
+);
diff --git a/test/built-ins/Temporal/TimeZone/from/timezone-string-leap-second.js b/test/built-ins/Temporal/TimeZone/from/timezone-string-leap-second.js
new file mode 100644
index 0000000000..6629f5aeb8
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/from/timezone-string-leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.from
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = Temporal.TimeZone.from(timeZone);
+assert.sameValue(result1.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = Temporal.TimeZone.from({ timeZone });
+assert.sameValue(result2.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.TimeZone.from(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.TimeZone.from({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..0e9d07bfb7
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getinstantfor
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.getInstantFor(arg);
+assert.sameValue(
+  result1.epochNanoseconds,
+  217_123_200_000_000_000n,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.getInstantFor(arg);
+assert.sameValue(
+  result2.epochNanoseconds,
+  217_123_200_000_000_000n,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/leap-second.js
new file mode 100644
index 0000000000..22945fe481
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getInstantFor/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getinstantfor
+description: Leap second is a valid ISO string for PlainDateTime
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.getInstantFor(arg);
+assert.sameValue(
+  result1.epochNanoseconds,
+  1_483_228_799_000_000_000n,
+  "leap second is a valid ISO string for PlainDateTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.getInstantFor(arg);
+assert.sameValue(
+  result2.epochNanoseconds,
+  1_483_228_799_000_000_000n,
+  "second: 60 is ignored in property bag for PlainDateTime"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/leap-second.js
new file mode 100644
index 0000000000..44cafb81c3
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getNextTransition/leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getnexttransition
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.getNextTransition(arg);
+assert.sameValue(
+  result,
+  null,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/leap-second.js
new file mode 100644
index 0000000000..417d2d4fd4
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getOffsetNanosecondsFor/leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getoffsetnanosecondsfor
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.getOffsetNanosecondsFor(arg);
+assert.sameValue(
+  result,
+  0,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/leap-second.js
new file mode 100644
index 0000000000..eac9e7c63c
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getOffsetStringFor/leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getoffsetstringfor
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.getOffsetStringFor(arg);
+assert.sameValue(
+  result,
+  "+00:00",
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/calendar-string-leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/calendar-string-leap-second.js
new file mode 100644
index 0000000000..927df49001
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/calendar-string-leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getplaindatetimefor
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.getPlainDateTimeFor(new Temporal.Instant(0n), arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = instance.getPlainDateTimeFor(new Temporal.Instant(0n), arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/leap-second.js
new file mode 100644
index 0000000000..f17224284a
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPlainDateTimeFor/leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getplaindatetimefor
+description: Leap second is a valid ISO string for Instant
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.getPlainDateTimeFor(arg);
+TemporalHelpers.assertPlainDateTime(
+  result,
+  2016, 12, "M12", 31, 23, 59, 59, 0, 0, 0,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..39b5d7ee9e
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getpossibleinstantsfor
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.getPossibleInstantsFor(arg);
+assert.compareArray(
+  result1.map(i => i.epochNanoseconds),
+  [217_123_200_000_000_000n],
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.getPossibleInstantsFor(arg);
+assert.compareArray(
+  result2.map(i => i.epochNanoseconds),
+  [217_123_200_000_000_000n],
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/leap-second.js
new file mode 100644
index 0000000000..79cb2a3732
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPossibleInstantsFor/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getpossibleinstantsfor
+description: Leap second is a valid ISO string for PlainDateTime
+includes: [compareArray.js]
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.getPossibleInstantsFor(arg);
+assert.compareArray(
+  result1.map(i => i.epochNanoseconds),
+  [1_483_228_799_000_000_000n],
+  "leap second is a valid ISO string for PlainDateTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.getPossibleInstantsFor(arg);
+assert.compareArray(
+  result2.map(i => i.epochNanoseconds),
+  [1_483_228_799_000_000_000n],
+  "second: 60 is ignored in property bag for PlainDateTime"
+);
diff --git a/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/leap-second.js b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/leap-second.js
new file mode 100644
index 0000000000..29d3b5d410
--- /dev/null
+++ b/test/built-ins/Temporal/TimeZone/prototype/getPreviousTransition/leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.timezone.prototype.getprevioustransition
+description: Leap second is a valid ISO string for Instant
+features: [Temporal]
+---*/
+
+const instance = new Temporal.TimeZone("UTC");
+
+const arg = "2016-12-31T23:59:60Z";
+const result = instance.getPreviousTransition(arg);
+assert.sameValue(
+  result,
+  null,
+  "leap second is a valid ISO string for Instant"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..8a6c34e0b8
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,24 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.compare
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const datetime = new Temporal.ZonedDateTime(217_123_200_000_000_000n, timeZone);
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, timeZone, calendar };
+const result1 = Temporal.ZonedDateTime.compare(arg, datetime);
+assert.sameValue(result1, 0, "leap second is a valid ISO string for calendar (first argument)");
+const result2 = Temporal.ZonedDateTime.compare(datetime, arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for calendar (second argument)");
+
+arg = { year: 1976, monthCode: "M11", day: 18, timeZone, calendar: { calendar } };
+const result3 = Temporal.ZonedDateTime.compare(arg, datetime);
+assert.sameValue(result3, 0, "leap second is a valid ISO string for calendar (nested property, first argument)");
+const result4 = Temporal.ZonedDateTime.compare(datetime, arg);
+assert.sameValue(result4, 0, "leap second is a valid ISO string for calendar (nested property, second argument)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js
new file mode 100644
index 0000000000..cdd1368336
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.compare
+description: Leap second is a valid ISO string for ZonedDateTime
+features: [Temporal]
+---*/
+
+const datetime = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, new Temporal.TimeZone("UTC"));
+
+let arg = "2016-12-31T23:59:60+00:00[UTC]";
+const result1 = Temporal.ZonedDateTime.compare(arg, datetime);
+assert.sameValue(result1, 0, "leap second is a valid ISO string for ZonedDateTime (first argument)");
+const result2 = Temporal.ZonedDateTime.compare(datetime, arg);
+assert.sameValue(result2, 0, "leap second is a valid ISO string for ZonedDateTime (second argument)");
+
+arg = "2000-05-02T12:34:56+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare(arg, datetime), "leap second in time zone name not valid (first argument)");
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare(datetime, arg), "leap second in time zone name not valid (second argument)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/compare/timezone-string-leap-second.js
new file mode 100644
index 0000000000..15726d7695
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/timezone-string-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.compare
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1588377600_000_000_000n, "UTC");
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = Temporal.ZonedDateTime.compare({ year: 2020, month: 5, day: 2, timeZone }, instance);
+assert.sameValue(result1, 0, "leap second is a valid ISO string for TimeZone (first argument)");
+const result2 = Temporal.ZonedDateTime.compare(instance, { year: 2020, month: 5, day: 2, timeZone });
+assert.sameValue(result2, 0, "leap second is a valid ISO string for TimeZone (second argument)");
+const result3 = Temporal.ZonedDateTime.compare({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }, instance);
+assert.sameValue(result3, 0, "leap second is a valid ISO string for TimeZone (nested property, first argument)");
+const result4 = Temporal.ZonedDateTime.compare(instance, { year: 2020, month: 5, day: 2, timeZone: { timeZone } });
+assert.sameValue(result4, 0, "leap second is a valid ISO string for TimeZone (nested property, second argument)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare({ year: 2020, month: 5, day: 2, timeZone }, instance), "leap second in time zone name not valid (first argument)");
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare(instance, { year: 2020, month: 5, day: 2, timeZone }), "leap second in time zone name not valid (second argument)");
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }, instance), "leap second in time zone name not valid (nested property, first argument)");
+assert.throws(RangeError, () => Temporal.ZonedDateTime.compare(instance, { year: 2020, month: 5, day: 2, timeZone: { timeZone } }), "leap second in time zone name not valid (nested property, second argument)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..2d68e15b72
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.from
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const result1 = Temporal.ZonedDateTime.from(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: { calendar } };
+const result2 = Temporal.ZonedDateTime.from(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/from/leap-second.js
new file mode 100644
index 0000000000..f7cf91d8e4
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/from/leap-second.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.from
+description: Leap second is a valid ISO string for ZonedDateTime
+features: [Temporal]
+---*/
+
+let arg = "2016-12-31T23:59:60+00:00[UTC]";
+const result = Temporal.ZonedDateTime.from(arg);
+assert.sameValue(
+  result.epochNanoseconds,
+  1_483_228_799_000_000_000n,
+  "leap second is a valid ISO string for ZonedDateTime"
+);
+
+arg = "2000-05-02T12:34:56+23:59[+23:59:60]";
+assert.throws(
+  RangeError,
+  () => Temporal.ZonedDateTime.from(arg),
+  "leap second in time zone name not valid"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/from/timezone-string-leap-second.js
new file mode 100644
index 0000000000..2b2a9eb311
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/from/timezone-string-leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.from
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = Temporal.ZonedDateTime.from({ year: 2000, month: 5, day: 2, timeZone });
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = Temporal.ZonedDateTime.from({ year: 2000, month: 5, day: 2, timeZone: { timeZone } });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => Temporal.ZonedDateTime.from({ year: 2000, month: 5, day: 2, timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => Temporal.ZonedDateTime.from({ year: 2000, month: 5, day: 2, timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..8957994ea2
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.equals
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const result1 = instance.equals(arg);
+assert.sameValue(
+  result1,
+  true,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: { calendar } };
+const result2 = instance.equals(arg);
+assert.sameValue(
+  result2,
+  true,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js
new file mode 100644
index 0000000000..cc57129d4e
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.equals
+description: Leap second is a valid ISO string for ZonedDateTime
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
+
+let arg = "2016-12-31T23:59:60+00:00[UTC]";
+const result = instance.equals(arg);
+assert.sameValue(
+  result,
+  true,
+  "leap second is a valid ISO string for ZonedDateTime"
+);
+
+arg = "2000-05-02T12:34:56+23:59[+23:59:60]";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "leap second in time zone name not valid"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/timezone-string-leap-second.js
new file mode 100644
index 0000000000..8470aacdbf
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/timezone-string-leap-second.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.equals
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1588377600_000_000_000n, new Temporal.TimeZone("UTC"));
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+assert(instance.equals({ year: 2020, month: 5, day: 2, timeZone }), "leap second is a valid ISO string for TimeZone");
+assert(instance.equals({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }), "leap second is a valid ISO String for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.equals({ year: 2020, month: 5, day: 2, timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.equals({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..a907504f4b
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const result1 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: { calendar } };
+const result2 = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js
new file mode 100644
index 0000000000..e3611500bb
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Leap second is a valid ISO string for ZonedDateTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
+
+let arg = "2016-12-31T23:59:60+00:00[UTC]";
+const result = instance.since(arg);
+TemporalHelpers.assertDuration(
+  result,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for ZonedDateTime"
+);
+
+arg = "2000-05-02T12:34:56+23:59[+23:59:60]";
+assert.throws(
+  RangeError,
+  () => instance.since(arg),
+  "leap second in time zone name not valid"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/timezone-string-leap-second.js
new file mode 100644
index 0000000000..5bce2e3547
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/timezone-string-leap-second.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const expectedTimeZone = "UTC";
+const instance = new Temporal.ZonedDateTime(0n, expectedTimeZone);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// These operations should produce expectedTimeZone, so the following operations
+// should not throw due to the time zones being different on the receiver and
+// the argument.
+
+instance.since({ year: 2020, month: 5, day: 2, timeZone });
+instance.since({ year: 2020, month: 5, day: 2, timeZone: { timeZone } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.since({ year: 2020, month: 5, day: 2, timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.since({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..df3b9989a8
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,30 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.until
+description: Leap second is a valid ISO string for a calendar in a property bag
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(0n, timeZone);
+
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const result1 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result1,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: { calendar } };
+const result2 = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result2,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js
new file mode 100644
index 0000000000..ffa342eff0
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/leap-second.js
@@ -0,0 +1,27 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.until
+description: Leap second is a valid ISO string for ZonedDateTime
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(1_483_228_799_000_000_000n, timeZone);
+
+let arg = "2016-12-31T23:59:60+00:00[UTC]";
+const result = instance.until(arg);
+TemporalHelpers.assertDuration(
+  result,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  "leap second is a valid ISO string for ZonedDateTime"
+);
+
+arg = "2000-05-02T12:34:56+23:59[+23:59:60]";
+assert.throws(
+  RangeError,
+  () => instance.until(arg),
+  "leap second in time zone name not valid"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/timezone-string-leap-second.js
new file mode 100644
index 0000000000..40dddba2e7
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/timezone-string-leap-second.js
@@ -0,0 +1,23 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.until
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const expectedTimeZone = "UTC";
+const instance = new Temporal.ZonedDateTime(0n, expectedTimeZone);
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+// These operations should produce expectedTimeZone, so the following operations
+// should not throw due to the time zones being different on the receiver and
+// the argument.
+
+instance.until({ year: 2020, month: 5, day: 2, timeZone });
+instance.until({ year: 2020, month: 5, day: 2, timeZone: { timeZone } });
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.until({ year: 2020, month: 5, day: 2, timeZone }), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.until({ year: 2020, month: 5, day: 2, timeZone: { timeZone } }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-string-leap-second.js
new file mode 100644
index 0000000000..29e229cc10
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-string-leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withcalendar
+description: Leap second is a valid ISO string for Calendar
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, "UTC", { id: "replace-me" });
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withCalendar(arg);
+assert.sameValue(
+  result1.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar"
+);
+
+arg = { calendar: "2016-12-31T23:59:60" };
+const result2 = instance.withCalendar(arg);
+assert.sameValue(
+  result2.calendar.id,
+  "iso8601",
+  "leap second is a valid ISO string for Calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..ebc5f7ce7f
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withplaindate
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const timeZone = new Temporal.TimeZone("UTC");
+const instance = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, timeZone);
+
+const calendar = "2016-12-31T23:59:60+00:00[UTC]";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.withPlainDate(arg);
+assert.sameValue(
+  result1.epochNanoseconds,
+  217_129_600_000_000_000n,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.withPlainDate(arg);
+assert.sameValue(
+  result2.epochNanoseconds,
+  217_129_600_000_000_000n,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/leap-second.js
new file mode 100644
index 0000000000..62e81954d3
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainDate/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withplaindate
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, "UTC");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withPlainDate(arg);
+assert.sameValue(
+  result1.epochNanoseconds,
+  1_483_148_800_000_000_000n,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.withPlainDate(arg);
+assert.sameValue(
+  result2.epochNanoseconds,
+  1_483_148_800_000_000_000n,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/leap-second.js
new file mode 100644
index 0000000000..9110c08d8f
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withPlainTime/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withplaintime
+description: Leap second is a valid ISO string for PlainTime
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, "UTC");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.withPlainTime(arg);
+assert.sameValue(
+  result1.epochNanoseconds,
+  1000079999_000_000_000n,
+  "leap second is a valid ISO string for PlainTime"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.withPlainTime(arg);
+assert.sameValue(
+  result2.epochNanoseconds,
+  1000079999_000_000_000n,
+  "second: 60 is ignored in property bag for PlainTime"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-leap-second.js
new file mode 100644
index 0000000000..93fc6d9d0e
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-leap-second.js
@@ -0,0 +1,20 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.withtimezone
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(0n, "UTC");
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = instance.withTimeZone(timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone");
+const result2 = instance.withTimeZone({ timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "leap second is a valid ISO string for TimeZone (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => instance.withTimeZone(timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => instance.withTimeZone({ timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/built-ins/Temporal/ZonedDateTime/timezone-string-leap-second.js b/test/built-ins/Temporal/ZonedDateTime/timezone-string-leap-second.js
new file mode 100644
index 0000000000..966502ef8f
--- /dev/null
+++ b/test/built-ins/Temporal/ZonedDateTime/timezone-string-leap-second.js
@@ -0,0 +1,19 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime
+description: Leap second is a valid ISO string for TimeZone
+features: [Temporal]
+---*/
+
+let timeZone = "2016-12-31T23:59:60+00:00[UTC]";
+
+const result1 = new Temporal.ZonedDateTime(0n, timeZone);
+assert.sameValue(result1.timeZone.id, "UTC", "Time zone string determined from bracket name");
+const result2 = new Temporal.ZonedDateTime(0n, { timeZone });
+assert.sameValue(result2.timeZone.id, "UTC", "Time zone string determined from bracket name (nested property)");
+
+timeZone = "2021-08-19T17:30:45.123456789+23:59[+23:59:60]";
+assert.throws(RangeError, () => new Temporal.ZonedDateTime(0n, timeZone), "leap second in time zone name not valid");
+assert.throws(RangeError, () => new Temporal.ZonedDateTime(0n, { timeZone }), "leap second in time zone name not valid (nested property)");
diff --git a/test/intl402/Temporal/Calendar/prototype/era/argument-propertybag-calendar-leap-second.js b/test/intl402/Temporal/Calendar/prototype/era/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..645159e747
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/era/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.era
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.era(arg);
+assert.sameValue(
+  result1,
+  undefined,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.era(arg);
+assert.sameValue(
+  result2,
+  undefined,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/intl402/Temporal/Calendar/prototype/era/leap-second.js b/test/intl402/Temporal/Calendar/prototype/era/leap-second.js
new file mode 100644
index 0000000000..42cb42f55a
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/era/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.era
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.era(arg);
+assert.sameValue(
+  result1,
+  undefined,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.era(arg);
+assert.sameValue(
+  result2,
+  undefined,
+  "second: 60 is ignored in property bag for PlainDate"
+);
diff --git a/test/intl402/Temporal/Calendar/prototype/eraYear/argument-propertybag-calendar-leap-second.js b/test/intl402/Temporal/Calendar/prototype/eraYear/argument-propertybag-calendar-leap-second.js
new file mode 100644
index 0000000000..1a2e15215b
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/eraYear/argument-propertybag-calendar-leap-second.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.erayear
+description: Leap second is a valid ISO string for a calendar in a property bag
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+const calendar = "2016-12-31T23:59:60";
+
+let arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const result1 = instance.eraYear(arg);
+assert.sameValue(
+  result1,
+  undefined,
+  "leap second is a valid ISO string for calendar"
+);
+
+arg = { year: 1976, monthCode: "M11", day: 18, calendar: { calendar } };
+const result2 = instance.eraYear(arg);
+assert.sameValue(
+  result2,
+  undefined,
+  "leap second is a valid ISO string for calendar (nested property)"
+);
diff --git a/test/intl402/Temporal/Calendar/prototype/eraYear/leap-second.js b/test/intl402/Temporal/Calendar/prototype/eraYear/leap-second.js
new file mode 100644
index 0000000000..3d1fabe6c2
--- /dev/null
+++ b/test/intl402/Temporal/Calendar/prototype/eraYear/leap-second.js
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.calendar.prototype.erayear
+description: Leap second is a valid ISO string for PlainDate
+features: [Temporal]
+---*/
+
+const instance = new Temporal.Calendar("iso8601");
+
+let arg = "2016-12-31T23:59:60";
+const result1 = instance.eraYear(arg);
+assert.sameValue(
+  result1,
+  undefined,
+  "leap second is a valid ISO string for PlainDate"
+);
+
+arg = { year: 2016, month: 12, day: 31, hour: 23, minute: 59, second: 60 };
+const result2 = instance.eraYear(arg);
+assert.sameValue(
+  result2,
+  undefined,
+  "second: 60 is ignored in property bag for PlainDate"
+);