diff --git a/test/built-ins/Temporal/PlainDate/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/calendar-case-insensitive.js
index ab5ef646fd..e4d4a588f2 100644
--- a/test/built-ins/Temporal/PlainDate/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/calendar-case-insensitive.js
@@ -7,7 +7,14 @@ description: Calendar names are case-insensitive
 features: [Temporal]
 ---*/
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 
 const result = new Temporal.PlainDate(2000, 5, 2, arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => new Temporal.PlainDate(2000, 5, 2, arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-case-insensitive.js
index 964ee7d1b4..e9f958888d 100644
--- a/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/compare/argument-propertybag-calendar-case-insensitive.js
@@ -7,10 +7,20 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result1 = Temporal.PlainDate.compare(arg, new Temporal.PlainDate(1976, 11, 18));
 assert.sameValue(result1, 0, "Calendar is case-insensitive (first argument)");
 const result2 = Temporal.PlainDate.compare(new Temporal.PlainDate(1976, 11, 18), arg);
 assert.sameValue(result2, 0, "Calendar is case-insensitive (second argument)");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDate.compare(arg, new Temporal.PlainDate(1976, 11, 18)),
+  "calendar ID is capital dotted I is not lowercased (first argument)"
+);
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDate.compare(new Temporal.PlainDate(1976, 11, 18), arg),
+  "calendar ID is capital dotted I is not lowercased (second argument)"
+);
diff --git a/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-case-insensitive.js
index a85901e4f2..2752ffe730 100644
--- a/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/from/argument-propertybag-calendar-case-insensitive.js
@@ -8,8 +8,13 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = Temporal.PlainDate.from(arg);
 TemporalHelpers.assertPlainDate(result, 1976, 11, "M11", 18, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDate.from(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index 199fd6601b..d62c5049fb 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -9,8 +9,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDate(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.equals(arg);
 assert.sameValue(result, true, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-case-insensitive.js
index 3afedb0745..47a3b67484 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/since/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDate(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.since(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.since(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-case-insensitive.js
index 71a5dd19f8..7dfae4b93d 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/until/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDate(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.until(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.until(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-case-insensitive.js
index 511b0df4f4..6a0ce65d69 100644
--- a/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDate/prototype/withCalendar/calendar-case-insensitive.js
@@ -31,6 +31,13 @@ const instance = new Temporal.PlainDate(1976, 11, 18, {
   yearOfWeek() {},
 });
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 const result = instance.withCalendar(arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.withCalendar(arg),
+  "calendar ID is ASCII-lowercased, capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/calendar-case-insensitive.js
index 2f096dd854..655ba0c242 100644
--- a/test/built-ins/Temporal/PlainDateTime/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/calendar-case-insensitive.js
@@ -7,7 +7,14 @@ description: Calendar names are case-insensitive
 features: [Temporal]
 ---*/
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 
 const result = new Temporal.PlainDateTime(2000, 5, 2, 15, 23, 30, 987, 654, 321, arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => new Temporal.PlainDateTime(2000, 5, 2, 15, 23, 30, 987, 654, 321, arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-case-insensitive.js
index 5ecd1cd2ef..7d89c703f8 100644
--- a/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/compare/argument-propertybag-calendar-case-insensitive.js
@@ -7,10 +7,20 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result1 = Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(1976, 11, 18));
 assert.sameValue(result1, 0, "Calendar is case-insensitive (first argument)");
 const result2 = Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(1976, 11, 18), arg);
 assert.sameValue(result2, 0, "Calendar is case-insensitive (second argument)");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDateTime.compare(arg, new Temporal.PlainDateTime(1976, 11, 18)),
+  "calendar ID is capital dotted I is not lowercased (first argument)"
+);
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDateTime.compare(new Temporal.PlainDateTime(1976, 11, 18), arg),
+  "calendar ID is capital dotted I is not lowercased (second argument)"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-case-insensitive.js
index d2ae9dfc0a..c3955ad95b 100644
--- a/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/from/argument-propertybag-calendar-case-insensitive.js
@@ -8,8 +8,13 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = Temporal.PlainDateTime.from(arg);
 TemporalHelpers.assertPlainDateTime(result, 1976, 11, "M11", 18, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainDateTime.from(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index b0ed162f6f..42c8d4d065 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -9,8 +9,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDateTime(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.equals(arg);
 assert.sameValue(result, true, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
index 1f8bac6a78..881eb8f0dc 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDateTime(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.since(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.since(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
index 2d9dd762ce..1c91b794e4 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainDateTime(1976, 11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1976, monthCode: "M11", day: 18, calendar };
+const arg = { year: 1976, monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.until(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.until(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-case-insensitive.js
index 9af65170f6..7545f4af25 100644
--- a/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainDateTime/prototype/withCalendar/calendar-case-insensitive.js
@@ -31,6 +31,13 @@ const instance = new Temporal.PlainDateTime(1976, 11, 18, 15, 23, 30, 123, 456,
   yearOfWeek() {},
 });
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 const result = instance.withCalendar(arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.withCalendar(arg),
+  "calendar ID is ASCII-lowercased, capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainMonthDay/calendar-case-insensitive.js
index e42d4d19c4..71ef3ac4f3 100644
--- a/test/built-ins/Temporal/PlainMonthDay/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainMonthDay/calendar-case-insensitive.js
@@ -7,7 +7,14 @@ description: Calendar names are case-insensitive
 features: [Temporal]
 ---*/
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 
 const result = new Temporal.PlainMonthDay(12, 15, arg, 1972);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => new Temporal.PlainMonthDay(12, 15, arg, 1972),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-case-insensitive.js
index bdd4634474..86adb3811a 100644
--- a/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainMonthDay/from/argument-propertybag-calendar-case-insensitive.js
@@ -8,8 +8,13 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { monthCode: "M11", day: 18, calendar };
+const arg = { monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = Temporal.PlainMonthDay.from(arg);
 TemporalHelpers.assertPlainMonthDay(result, "M11", 18, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainMonthDay.from(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index bafa6df764..d4df95f64a 100644
--- a/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainMonthDay/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -9,8 +9,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainMonthDay(11, 18);
 
-const calendar = "IsO8601";
-
-const arg = { monthCode: "M11", day: 18, calendar };
+const arg = { monthCode: "M11", day: 18, calendar: "IsO8601" };
 const result = instance.equals(arg);
 assert.sameValue(result, true, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/calendar-case-insensitive.js
index 7c6d96efce..6a398ef4bc 100644
--- a/test/built-ins/Temporal/PlainYearMonth/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/calendar-case-insensitive.js
@@ -7,7 +7,14 @@ description: Calendar names are case-insensitive
 features: [Temporal]
 ---*/
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 
 const result = new Temporal.PlainYearMonth(2000, 5, arg, 1);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => new Temporal.PlainYearMonth(2000, 5, arg, 1),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/compare/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/compare/argument-propertybag-calendar-case-insensitive.js
index b6390fa434..a32ce0c92a 100644
--- a/test/built-ins/Temporal/PlainYearMonth/compare/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/compare/argument-propertybag-calendar-case-insensitive.js
@@ -7,10 +7,20 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 2019, monthCode: "M06", calendar };
+const arg = { year: 2019, monthCode: "M06", calendar: "IsO8601" };
 const result1 = Temporal.PlainYearMonth.compare(arg, new Temporal.PlainYearMonth(2019, 6));
 assert.sameValue(result1, 0, "Calendar is case-insensitive (first argument)");
 const result2 = Temporal.PlainYearMonth.compare(new Temporal.PlainYearMonth(2019, 6), arg);
 assert.sameValue(result2, 0, "Calendar is case-insensitive (second argument)");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainYearMonth.compare(arg, new Temporal.PlainYearMonth(2019, 6)),
+  "calendar ID is capital dotted I is not lowercased (first argument)"
+);
+assert.throws(
+  RangeError,
+  () => Temporal.PlainYearMonth.compare(new Temporal.PlainYearMonth(2019, 6), arg),
+  "calendar ID is capital dotted I is not lowercased (second argument)"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-case-insensitive.js
index addc6aeef4..8d13288689 100644
--- a/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/from/argument-propertybag-calendar-case-insensitive.js
@@ -8,8 +8,13 @@ includes: [temporalHelpers.js]
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
-const arg = { year: 2019, monthCode: "M06", calendar };
+const arg = { year: 2019, monthCode: "M06", calendar: "IsO8601" };
 const result = Temporal.PlainYearMonth.from(arg);
 TemporalHelpers.assertPlainYearMonth(result, 2019, 6, "M06", "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.PlainYearMonth.from(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index 2d7bedf2f3..47d7c353fc 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -9,8 +9,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainYearMonth(2019, 6);
 
-const calendar = "IsO8601";
-
-const arg = { year: 2019, monthCode: "M06", calendar };
+const arg = { year: 2019, monthCode: "M06", calendar: "IsO8601" };
 const result = instance.equals(arg);
 assert.sameValue(result, true, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-case-insensitive.js
index b290e51b50..3364189dbf 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/since/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainYearMonth(2019, 6);
 
-const calendar = "IsO8601";
-
-const arg = { year: 2019, monthCode: "M06", calendar };
+const arg = { year: 2019, monthCode: "M06", calendar: "IsO8601" };
 const result = instance.since(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.since(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-case-insensitive.js
index a708ef9313..074fd1b040 100644
--- a/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/PlainYearMonth/prototype/until/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 
 const instance = new Temporal.PlainYearMonth(2019, 6);
 
-const calendar = "IsO8601";
-
-const arg = { year: 2019, monthCode: "M06", calendar };
+const arg = { year: 2019, monthCode: "M06", calendar: "IsO8601" };
 const result = instance.until(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.until(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/calendar-case-insensitive.js
index f7b725c797..d9df704f27 100644
--- a/test/built-ins/Temporal/ZonedDateTime/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/calendar-case-insensitive.js
@@ -7,7 +7,14 @@ description: Calendar names are case-insensitive
 features: [Temporal]
 ---*/
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 
 const result = new Temporal.ZonedDateTime(0n, "UTC", arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => new Temporal.ZonedDateTime(0n, "UTC", arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
index 986ede0cbc..ca19916005 100644
--- a/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-calendar-case-insensitive.js
@@ -7,13 +7,23 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
 const timeZone = new Temporal.TimeZone("UTC");
 const datetime = new Temporal.ZonedDateTime(0n, timeZone);
 
-const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result1 = Temporal.ZonedDateTime.compare(arg, datetime);
 assert.sameValue(result1, 0, "Calendar is case-insensitive (first argument)");
 const result2 = Temporal.ZonedDateTime.compare(datetime, arg);
 assert.sameValue(result2, 0, "Calendar is case-insensitive (second argument)");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.ZonedDateTime.compare(arg, datetime),
+  "calendar ID is capital dotted I is not lowercased (first argument)"
+);
+assert.throws(
+  RangeError,
+  () => Temporal.ZonedDateTime.compare(datetime, arg),
+  "calendar ID is capital dotted I is not lowercased (second argument)"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
index 2efae5a2ba..3baa8ff31f 100644
--- a/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/from/argument-propertybag-calendar-case-insensitive.js
@@ -7,9 +7,14 @@ description: The calendar name is case-insensitive
 features: [Temporal]
 ---*/
 
-const calendar = "IsO8601";
-
 const timeZone = new Temporal.TimeZone("UTC");
-const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result = Temporal.ZonedDateTime.from(arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => Temporal.ZonedDateTime.from(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
index b4f97b6629..fe11b2b851 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-calendar-case-insensitive.js
@@ -10,8 +10,13 @@ features: [Temporal]
 const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result = instance.equals(arg);
 assert.sameValue(result, true, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.equals(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
index 1d341ebc14..bc37379656 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-calendar-case-insensitive.js
@@ -11,8 +11,13 @@ features: [Temporal]
 const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result = instance.since(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.since(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
index c822b03b28..1dd8006d86 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-calendar-case-insensitive.js
@@ -11,8 +11,13 @@ features: [Temporal]
 const timeZone = new Temporal.TimeZone("UTC");
 const instance = new Temporal.ZonedDateTime(0n, timeZone);
 
-const calendar = "IsO8601";
-
-const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar };
+const arg = { year: 1970, monthCode: "M01", day: 1, timeZone, calendar: "IsO8601" };
 const result = instance.until(arg);
 TemporalHelpers.assertDuration(result, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Calendar is case-insensitive");
+
+arg.calendar = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.until(arg),
+  "calendar ID is capital dotted I is not lowercased"
+);
diff --git a/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive.js b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive.js
index 5fdfeee782..69ae9b6229 100644
--- a/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive.js
+++ b/test/built-ins/Temporal/ZonedDateTime/prototype/withCalendar/calendar-case-insensitive.js
@@ -31,6 +31,13 @@ const instance = new Temporal.ZonedDateTime(1_000_000_000_000_000_000n, "UTC", {
   yearOfWeek() {},
 });
 
-const arg = "iSo8601";
+let arg = "iSo8601";
 const result = instance.withCalendar(arg);
 assert.sameValue(result.calendarId, "iso8601", "Calendar is case-insensitive");
+
+arg = "\u0130SO8601";
+assert.throws(
+  RangeError,
+  () => instance.withCalendar(arg),
+  "calendar ID is ASCII-lowercased, capital dotted I is not lowercased"
+);
diff --git a/test/intl402/Temporal/PlainDate/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/canonicalize-calendar.js
new file mode 100644
index 0000000000..95dde46890
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/canonicalize-calendar.js
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const result = new Temporal.PlainDate(2024, 7, 2, "islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainDate/from/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/from/canonicalize-calendar.js
new file mode 100644
index 0000000000..b9e7436062
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/from/canonicalize-calendar.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+[
+  "2024-07-02[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = Temporal.PlainDate.from(arg);
+  assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDate/prototype/equals/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/prototype/equals/canonicalize-calendar.js
new file mode 100644
index 0000000000..e6f136502f
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/equals/canonicalize-calendar.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2024, 7, 2, "islamic-civil");
+
+[
+  "2024-07-02[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, calendar: "islamicc" },
+].forEach((arg) => assert(instance.equals(arg), "calendar ID is canonicalized"));
diff --git a/test/intl402/Temporal/PlainDate/prototype/since/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/prototype/since/canonicalize-calendar.js
new file mode 100644
index 0000000000..992d2865b0
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/since/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2024, 7, 2, "islamic-civil");
+
+[
+  "2024-07-02[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.since(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDate/prototype/until/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/prototype/until/canonicalize-calendar.js
new file mode 100644
index 0000000000..880a598de4
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/until/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2024, 7, 2, "islamic-civil");
+
+[
+  "2024-07-02[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.until(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDate/prototype/withCalendar/canonicalize-calendar.js b/test/intl402/Temporal/PlainDate/prototype/withCalendar/canonicalize-calendar.js
new file mode 100644
index 0000000000..876495a9c7
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/withCalendar/canonicalize-calendar.js
@@ -0,0 +1,12 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDate(2024, 7, 2);
+const result = instance.withCalendar("islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainDateTime/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/canonicalize-calendar.js
new file mode 100644
index 0000000000..f538c41062
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/canonicalize-calendar.js
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const result = new Temporal.PlainDateTime(2024, 7, 2, 12, 34, 56, 987, 654, 321, "islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainDateTime/from/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/from/canonicalize-calendar.js
new file mode 100644
index 0000000000..8ef0f06dc7
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/from/canonicalize-calendar.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+[
+  "2024-07-02T12:34[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = Temporal.PlainDateTime.from(arg);
+  assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/equals/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/prototype/equals/canonicalize-calendar.js
new file mode 100644
index 0000000000..32448d96f6
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/equals/canonicalize-calendar.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2024, 7, 2, 12, 34, 0, 0, 0, 0, "islamic-civil");
+
+[
+  "2024-07-02T12:34[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc" },
+].forEach((arg) => assert(instance.equals(arg), "calendar ID is canonicalized"));
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/since/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/prototype/since/canonicalize-calendar.js
new file mode 100644
index 0000000000..00fbf63b91
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/since/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2024, 7, 2, 12, 34, 0, 0, 0, 0, "islamic-civil");
+
+[
+  "2024-07-02T12:34[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.since(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/until/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/prototype/until/canonicalize-calendar.js
new file mode 100644
index 0000000000..172ef87b1e
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/until/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2024, 7, 2, 12, 34, 0, 0, 0, 0, "islamic-civil");
+
+[
+  "2024-07-02T12:34[u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.until(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/withCalendar/canonicalize-calendar.js b/test/intl402/Temporal/PlainDateTime/prototype/withCalendar/canonicalize-calendar.js
new file mode 100644
index 0000000000..2deca2c79d
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/withCalendar/canonicalize-calendar.js
@@ -0,0 +1,12 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainDateTime(2024, 7, 2, 12, 34);
+const result = instance.withCalendar("islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainMonthDay/canonicalize-calendar.js b/test/intl402/Temporal/PlainMonthDay/canonicalize-calendar.js
new file mode 100644
index 0000000000..8d3a518adc
--- /dev/null
+++ b/test/intl402/Temporal/PlainMonthDay/canonicalize-calendar.js
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainmonthday
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const result = new Temporal.PlainMonthDay(2, 11, "islamicc", 1972);
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainMonthDay/from/canonicalize-calendar.js b/test/intl402/Temporal/PlainMonthDay/from/canonicalize-calendar.js
new file mode 100644
index 0000000000..41770f3962
--- /dev/null
+++ b/test/intl402/Temporal/PlainMonthDay/from/canonicalize-calendar.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+[
+  "1972-02-11[u-ca=islamicc]",
+  { monthCode: "M12", day: 25, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = Temporal.PlainMonthDay.from(arg);
+  assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainMonthDay/prototype/equals/canonicalize-calendar.js b/test/intl402/Temporal/PlainMonthDay/prototype/equals/canonicalize-calendar.js
new file mode 100644
index 0000000000..603b582c24
--- /dev/null
+++ b/test/intl402/Temporal/PlainMonthDay/prototype/equals/canonicalize-calendar.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainMonthDay(2, 11, "islamic-civil", 1972);
+
+[
+  "1972-02-11[u-ca=islamicc]",
+  { monthCode: "M12", day: 25, calendar: "islamicc" },
+].forEach((arg) => assert(instance.equals(arg), "calendar ID is canonicalized"));
diff --git a/test/intl402/Temporal/PlainYearMonth/canonicalize-calendar.js b/test/intl402/Temporal/PlainYearMonth/canonicalize-calendar.js
new file mode 100644
index 0000000000..b1e7d417a2
--- /dev/null
+++ b/test/intl402/Temporal/PlainYearMonth/canonicalize-calendar.js
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plainyearmonth
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const result = new Temporal.PlainYearMonth(2024, 6, "islamicc", 8);
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/PlainYearMonth/from/canonicalize-calendar.js b/test/intl402/Temporal/PlainYearMonth/from/canonicalize-calendar.js
new file mode 100644
index 0000000000..93326b44bf
--- /dev/null
+++ b/test/intl402/Temporal/PlainYearMonth/from/canonicalize-calendar.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+[
+  "2024-06-08[u-ca=islamicc]",
+  { year: 1445, month: 12, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = Temporal.PlainYearMonth.from(arg);
+  assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainYearMonth/prototype/equals/canonicalize-calendar.js b/test/intl402/Temporal/PlainYearMonth/prototype/equals/canonicalize-calendar.js
new file mode 100644
index 0000000000..c026dafe61
--- /dev/null
+++ b/test/intl402/Temporal/PlainYearMonth/prototype/equals/canonicalize-calendar.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2024, 6, "islamic-civil", 8);
+
+[
+  "2024-06-08[u-ca=islamicc]",
+  { year: 1445, month: 12, calendar: "islamicc" },
+].forEach((arg) => assert(instance.equals(arg), "calendar ID is canonicalized"));
diff --git a/test/intl402/Temporal/PlainYearMonth/prototype/since/canonicalize-calendar.js b/test/intl402/Temporal/PlainYearMonth/prototype/since/canonicalize-calendar.js
new file mode 100644
index 0000000000..b623c667fa
--- /dev/null
+++ b/test/intl402/Temporal/PlainYearMonth/prototype/since/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2024, 6, "islamic-civil", 8);
+
+[
+  "2024-06-08[u-ca=islamicc]",
+  { year: 1445, month: 12, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.since(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/PlainYearMonth/prototype/until/canonicalize-calendar.js b/test/intl402/Temporal/PlainYearMonth/prototype/until/canonicalize-calendar.js
new file mode 100644
index 0000000000..2135db7095
--- /dev/null
+++ b/test/intl402/Temporal/PlainYearMonth/prototype/until/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.PlainYearMonth(2024, 6, "islamic-civil", 8);
+
+[
+  "2024-06-08[u-ca=islamicc]",
+  { year: 1445, month: 12, calendar: "islamicc" },
+].forEach((arg) => {
+  const result = instance.until(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/ZonedDateTime/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/canonicalize-calendar.js
new file mode 100644
index 0000000000..a1ddae9da2
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/canonicalize-calendar.js
@@ -0,0 +1,11 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const result = new Temporal.ZonedDateTime(1719923640_000_000_000n, "UTC", "islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/intl402/Temporal/ZonedDateTime/from/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/from/canonicalize-calendar.js
new file mode 100644
index 0000000000..9cd35739d0
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/from/canonicalize-calendar.js
@@ -0,0 +1,16 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+[
+  "2024-07-02T12:34+00:00[UTC][u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc", timeZone: "UTC" },
+].forEach((arg) => {
+  const result = Temporal.ZonedDateTime.from(arg);
+  assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/equals/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/prototype/equals/canonicalize-calendar.js
new file mode 100644
index 0000000000..1943a68101
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/equals/canonicalize-calendar.js
@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1719923640_000_000_000n, "UTC", "islamic-civil");
+
+[
+  "2024-07-02T12:34+00:00[UTC][u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc", timeZone: "UTC" },
+].forEach((arg) => assert(instance.equals(arg), "calendar ID is canonicalized"));
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/since/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/prototype/since/canonicalize-calendar.js
new file mode 100644
index 0000000000..1a5894aa8a
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/since/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1719923640_000_000_000n, "UTC", "islamic-civil");
+
+[
+  "2024-07-02T12:34+00:00[UTC][u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc", timeZone: "UTC" },
+].forEach((arg) => {
+  const result = instance.since(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/until/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/prototype/until/canonicalize-calendar.js
new file mode 100644
index 0000000000..a950b1147f
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/until/canonicalize-calendar.js
@@ -0,0 +1,18 @@
+// Copyright (C) 2024 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: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1719923640_000_000_000n, "UTC", "islamic-civil");
+
+[
+  "2024-07-02T12:34+00:00[UTC][u-ca=islamicc]",
+  { year: 1445, month: 12, day: 25, hour: 12, minute: 34, calendar: "islamicc", timeZone: "UTC" },
+].forEach((arg) => {
+  const result = instance.until(arg);  // would throw if calendar was not canonicalized
+  assert(result.blank, "calendar ID is canonicalized");
+});
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/withCalendar/canonicalize-calendar.js b/test/intl402/Temporal/ZonedDateTime/prototype/withCalendar/canonicalize-calendar.js
new file mode 100644
index 0000000000..67199ab360
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/withCalendar/canonicalize-calendar.js
@@ -0,0 +1,12 @@
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zonedatetime.prototype.withcalendar
+description: Calendar ID is canonicalized
+features: [Temporal]
+---*/
+
+const instance = new Temporal.ZonedDateTime(1719923640_000_000_000n, "UTC");
+const result = instance.withCalendar("islamicc");
+assert.sameValue(result.calendarId, "islamic-civil", "calendar ID is canonicalized");
diff --git a/test/staging/Intl402/Temporal/old/islamic-calendars.js b/test/staging/Intl402/Temporal/old/islamic-calendars.js
index 34ff2755f0..47bad664c2 100644
--- a/test/staging/Intl402/Temporal/old/islamic-calendars.js
+++ b/test/staging/Intl402/Temporal/old/islamic-calendars.js
@@ -3,7 +3,7 @@
 
 /*---
 esid: sec-temporal-intl
-description: Islamic calendars (note there are 6 variants)
+description: Islamic calendars (note there are 5 variants)
 features: [Temporal]
 ---*/
 
@@ -37,15 +37,6 @@ const tests = [
     isoMonth: 7,
     isoDay: 19
   },
-  {
-    calendar: "islamicc", // deprecated version of islamic-civil
-    inLeapYear: true,
-    daysInYear: 355,
-    daysInMonth12: 30,
-    isoYear: 2023,
-    isoMonth: 7,
-    isoDay: 19
-  },
   {
     calendar: "islamic-rgsa",
     inLeapYear: false,