diff --git a/test/intl402/Temporal/PlainDate/prototype/add/basic-chinese.js b/test/intl402/Temporal/PlainDate/prototype/add/basic-chinese.js
new file mode 100644
index 0000000000..2c3afe8662
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/add/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.add
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M11", day: 1, calendar }, options).add(duration1),
+  2019, 12, "M12", 1, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M12", day: 1, calendar }, options).add(duration1),
+  2020, 1, "M01", 1, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).add(months2weeks3),
+  2021, 3, "M03", 22, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).add(months2weeks3),
+  2022, 3, "M03", 21, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).add(days10),
+  2021, 1, "M01", 11, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 29, calendar }, options).add(days10),
+  2021, 2, "M02", 10, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).add(days10),
+  2022, 1, "M01", 10, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/add/basic-dangi.js b/test/intl402/Temporal/PlainDate/prototype/add/basic-dangi.js
new file mode 100644
index 0000000000..8e32a15c21
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/add/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.add
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M11", day: 1, calendar }, options).add(duration1),
+  2019, 12, "M12", 1, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M12", day: 1, calendar }, options).add(duration1),
+  2020, 1, "M01", 1, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).add(months2weeks3),
+  2021, 3, "M03", 22, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).add(months2weeks3),
+  2022, 3, "M03", 21, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).add(days10),
+  2021, 1, "M01", 11, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 29, calendar }, options).add(days10),
+  2021, 2, "M02", 10, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).add(days10),
+  2022, 1, "M01", 10, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/add/leap-months-chinese.js b/test/intl402/Temporal/PlainDate/prototype/add/leap-months-chinese.js
new file mode 100644
index 0000000000..d7ba584c2e
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/add/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.add
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M01", day: 1, calendar }, options).add(years1),
+  2020, 1, "M01", 1, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1966, monthCode: "M03L", day: 1, calendar }, options).add(years1),
+  1967, 3, "M03", 1, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1938, monthCode: "M07L", day: 30, calendar }, options).add(years1),
+  1939, 7, "M07", 29, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 1, calendar }, options).add(months1),
+  1947, 4, "M03", 1, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 1, calendar }, options).add(months1),
+  1955, 5, "M04", 1, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDate.from({ year: 2020, monthCode: "M03", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.add(months1),
+  2020, 4, "M04", 1, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.add(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.add(new Temporal.Duration(0, 3)),
+  2020, 6, "M05", 1, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDate.from({ year: 2020, monthCode: "M06", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.add(months1n),
+  2020, 6, "M05", 1, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.add(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.add(new Temporal.Duration(0, -3)),
+  2020, 4, "M04", 1, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M05", day: 1, calendar }, options).add(months1n),
+  2020, 5, "M04L", 1, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M04L", day: 1, calendar }, options).add(months1n),
+  2020, 4, "M04", 1, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).add(months2weeks3),
+  1947, 6, "M05", 20, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).add(months2weeks3),
+  1955, 7, "M06", 21, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M01", day: 29, calendar }, options).add(months2weeks3),
+  1947, 4, "M03", 21, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M06", day: 29, calendar }, options).add(months2weeks3),
+  1955, 10, "M09", 20, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).add(days10),
+  1955, 5, "M04", 10, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).add(days10),
+  1947, 4, "M03", 10, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/add/leap-months-dangi.js b/test/intl402/Temporal/PlainDate/prototype/add/leap-months-dangi.js
new file mode 100644
index 0000000000..4feb90a6b4
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/add/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.add
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M01", day: 1, calendar }, options).add(years1),
+  2020, 1, "M01", 1, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1966, monthCode: "M03L", day: 1, calendar }, options).add(years1),
+  1967, 3, "M03", 1, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1938, monthCode: "M07L", day: 30, calendar }, options).add(years1),
+  1939, 7, "M07", 29, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 1, calendar }, options).add(months1),
+  1947, 4, "M03", 1, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 1, calendar }, options).add(months1),
+  1955, 5, "M04", 1, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDate.from({ year: 2020, monthCode: "M03", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.add(months1),
+  2020, 4, "M04", 1, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.add(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.add(new Temporal.Duration(0, 3)),
+  2020, 6, "M05", 1, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDate.from({ year: 2020, monthCode: "M06", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.add(months1n),
+  2020, 6, "M05", 1, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.add(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.add(new Temporal.Duration(0, -3)),
+  2020, 4, "M04", 1, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M05", day: 1, calendar }, options).add(months1n),
+  2020, 5, "M04L", 1, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M04L", day: 1, calendar }, options).add(months1n),
+  2020, 4, "M04", 1, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).add(months2weeks3),
+  1947, 6, "M05", 20, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).add(months2weeks3),
+  1955, 7, "M06", 21, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M01", day: 29, calendar }, options).add(months2weeks3),
+  1947, 4, "M03", 21, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M06", day: 29, calendar }, options).add(months2weeks3),
+  1955, 10, "M09", 20, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).add(days10),
+  1955, 5, "M04", 10, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).add(days10),
+  1947, 4, "M03", 10, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/subtract/basic-chinese.js b/test/intl402/Temporal/PlainDate/prototype/subtract/basic-chinese.js
new file mode 100644
index 0000000000..7e85631ac1
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/subtract/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.subtract
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M11", day: 1, calendar }, options).subtract(duration1),
+  2019, 12, "M12", 1, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M12", day: 1, calendar }, options).subtract(duration1),
+  2020, 1, "M01", 1, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).subtract(months2weeks3),
+  2021, 3, "M03", 22, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).subtract(months2weeks3),
+  2022, 3, "M03", 21, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).subtract(days10),
+  2021, 1, "M01", 11, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 29, calendar }, options).subtract(days10),
+  2021, 2, "M02", 10, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).subtract(days10),
+  2022, 1, "M01", 10, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/subtract/basic-dangi.js b/test/intl402/Temporal/PlainDate/prototype/subtract/basic-dangi.js
new file mode 100644
index 0000000000..1fc3f3c77e
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/subtract/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.subtract
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M11", day: 1, calendar }, options).subtract(duration1),
+  2019, 12, "M12", 1, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M12", day: 1, calendar }, options).subtract(duration1),
+  2020, 1, "M01", 1, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).subtract(months2weeks3),
+  2021, 3, "M03", 22, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).subtract(months2weeks3),
+  2022, 3, "M03", 21, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 1, calendar }, options).subtract(days10),
+  2021, 1, "M01", 11, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M01", day: 29, calendar }, options).subtract(days10),
+  2021, 2, "M02", 10, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2021, monthCode: "M12", day: 29, calendar }, options).subtract(days10),
+  2022, 1, "M01", 10, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-chinese.js b/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-chinese.js
new file mode 100644
index 0000000000..a47c7f1194
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.subtract
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M01", day: 1, calendar }, options).subtract(years1),
+  2020, 1, "M01", 1, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1966, monthCode: "M03L", day: 1, calendar }, options).subtract(years1),
+  1967, 3, "M03", 1, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1938, monthCode: "M07L", day: 30, calendar }, options).subtract(years1),
+  1939, 7, "M07", 29, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 1, calendar }, options).subtract(months1),
+  1947, 4, "M03", 1, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 1, calendar }, options).subtract(months1),
+  1955, 5, "M04", 1, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDate.from({ year: 2020, monthCode: "M03", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.subtract(months1),
+  2020, 4, "M04", 1, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.subtract(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.subtract(new Temporal.Duration(0, -3)),
+  2020, 6, "M05", 1, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDate.from({ year: 2020, monthCode: "M06", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.subtract(months1n),
+  2020, 6, "M05", 1, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.subtract(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.subtract(new Temporal.Duration(0, 3)),
+  2020, 4, "M04", 1, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M05", day: 1, calendar }, options).subtract(months1n),
+  2020, 5, "M04L", 1, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M04L", day: 1, calendar }, options).subtract(months1n),
+  2020, 4, "M04", 1, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).subtract(months2weeks3),
+  1947, 6, "M05", 20, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).subtract(months2weeks3),
+  1955, 7, "M06", 21, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M01", day: 29, calendar }, options).subtract(months2weeks3),
+  1947, 4, "M03", 21, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M06", day: 29, calendar }, options).subtract(months2weeks3),
+  1955, 10, "M09", 20, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).subtract(days10),
+  1955, 5, "M04", 10, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).subtract(days10),
+  1947, 4, "M03", 10, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-dangi.js b/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-dangi.js
new file mode 100644
index 0000000000..409f058cef
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/subtract/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindate.prototype.subtract
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2019, monthCode: "M01", day: 1, calendar }, options).subtract(years1),
+  2020, 1, "M01", 1, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1966, monthCode: "M03L", day: 1, calendar }, options).subtract(years1),
+  1967, 3, "M03", 1, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1938, monthCode: "M07L", day: 30, calendar }, options).subtract(years1),
+  1939, 7, "M07", 29, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 1, calendar }, options).subtract(months1),
+  1947, 4, "M03", 1, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 1, calendar }, options).subtract(months1),
+  1955, 5, "M04", 1, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDate.from({ year: 2020, monthCode: "M03", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.subtract(months1),
+  2020, 4, "M04", 1, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.subtract(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date1.subtract(new Temporal.Duration(0, -3)),
+  2020, 6, "M05", 1, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDate.from({ year: 2020, monthCode: "M06", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.subtract(months1n),
+  2020, 6, "M05", 1, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.subtract(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDate(
+  date2.subtract(new Temporal.Duration(0, 3)),
+  2020, 4, "M04", 1, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M05", day: 1, calendar }, options).subtract(months1n),
+  2020, 5, "M04L", 1, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 2020, monthCode: "M04L", day: 1, calendar }, options).subtract(months1n),
+  2020, 4, "M04", 1, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).subtract(months2weeks3),
+  1947, 6, "M05", 20, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).subtract(months2weeks3),
+  1955, 7, "M06", 21, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M01", day: 29, calendar }, options).subtract(months2weeks3),
+  1947, 4, "M03", 21, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M06", day: 29, calendar }, options).subtract(months2weeks3),
+  1955, 10, "M09", 20, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1955, monthCode: "M03L", day: 30, calendar }, options).subtract(days10),
+  1955, 5, "M04", 10, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDate(
+  Temporal.PlainDate.from({ year: 1947, monthCode: "M02L", day: 29, calendar }, options).subtract(days10),
+  1947, 4, "M03", 10, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/add/basic-chinese.js b/test/intl402/Temporal/PlainDateTime/prototype/add/basic-chinese.js
new file mode 100644
index 0000000000..b302a658ef
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/add/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.add
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, calendar }, options).add(duration1),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, calendar }, options).add(duration1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(days10),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/add/basic-dangi.js b/test/intl402/Temporal/PlainDateTime/prototype/add/basic-dangi.js
new file mode 100644
index 0000000000..8bbcc9960f
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/add/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.add
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, calendar }, options).add(duration1),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, calendar }, options).add(duration1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(days10),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-chinese.js b/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-chinese.js
new file mode 100644
index 0000000000..4156c5bb48
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.add
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(years1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).add(years1),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, calendar }, options).add(years1),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(months1),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 3)),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(months1n),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -3)),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, calendar }, options).add(months1n),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1n),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).add(days10),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-dangi.js b/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-dangi.js
new file mode 100644
index 0000000000..d05ac34d20
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/add/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.add
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).add(years1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).add(years1),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, calendar }, options).add(years1),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(months1),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 3)),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(months1n),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -3)),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, calendar }, options).add(months1n),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, calendar }, options).add(months1n),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, calendar }, options).add(months2weeks3),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).add(days10),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).add(days10),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-chinese.js b/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-chinese.js
new file mode 100644
index 0000000000..c851869014
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.subtract
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, calendar }, options).subtract(duration1),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, calendar }, options).subtract(duration1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-dangi.js b/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-dangi.js
new file mode 100644
index 0000000000..bbd67f392e
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/subtract/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.subtract
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, calendar }, options).subtract(duration1),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, calendar }, options).subtract(duration1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-chinese.js b/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-chinese.js
new file mode 100644
index 0000000000..f62abb36b8
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.subtract
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(months1),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -3)),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(months1n),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 3)),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1n),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1n),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-dangi.js b/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-dangi.js
new file mode 100644
index 0000000000..d449ad1fcb
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/subtract/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.plaindatetime.prototype.subtract
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(years1),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(months1),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -3)),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.PlainDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(months1n),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 2)),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 3)),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1n),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, calendar }, options).subtract(months1n),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, calendar }, options).subtract(months2weeks3),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.PlainDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, calendar }, options).subtract(days10),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-chinese.js b/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-chinese.js
new file mode 100644
index 0000000000..e9f4bfa09c
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.add
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(duration1).toPlainDateTime(),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(duration1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-dangi.js b/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-dangi.js
new file mode 100644
index 0000000000..5c1af6243e
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/add/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.add
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(duration1).toPlainDateTime(),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(duration1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-chinese.js b/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-chinese.js
new file mode 100644
index 0000000000..af4c72495f
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.add
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1).toPlainDateTime(),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1).toPlainDateTime(),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(months1).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 3)).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(months1n).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -3)).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1n).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1n).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-dangi.js b/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-dangi.js
new file mode 100644
index 0000000000..359858820e
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/add/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.add
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(years1).toPlainDateTime(),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, 1);
+const months1n = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1).toPlainDateTime(),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1).toPlainDateTime(),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(months1).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.add(new Temporal.Duration(0, 3)).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(months1n).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.add(new Temporal.Duration(0, -3)).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1n).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months1n).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ 2, /* weeks = */ 3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(months2weeks3).toPlainDateTime(),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ 10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).add(days10).toPlainDateTime(),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-chinese.js b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-chinese.js
new file mode 100644
index 0000000000..4e64ac4b95
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-chinese.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.subtract
+description: Basic addition and subtraction in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(duration1).toPlainDateTime(),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(duration1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-dangi.js b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-dangi.js
new file mode 100644
index 0000000000..3e840968f6
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/basic-dangi.js
@@ -0,0 +1,61 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.subtract
+description: Basic addition and subtraction in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+// Months
+
+const duration1 = new Temporal.Duration(0, -1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M11", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(duration1).toPlainDateTime(),
+  2019, 12, "M12", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M12", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(duration1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 month, with result in next year"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  2021, 3, "M03", 22, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from non-leap day/month, ending in same year"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  2022, 3, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from end of year to next year"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2021, 1, "M01", 11, 12, 34, 0, 0, 0, 0, "add 10 days, ending in same month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2021, 2, "M02", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2021, monthCode: "M12", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  2022, 1, "M01", 10, 12, 34, 0, 0, 0, 0, "add 10 days, ending in following year"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-chinese.js b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-chinese.js
new file mode 100644
index 0000000000..d9470c7021
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-chinese.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.subtract
+description: Arithmetic around leap months in the chinese calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "chinese";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1).toPlainDateTime(),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1).toPlainDateTime(),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(months1).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -3)).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(months1n).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 3)).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1n).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1n).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-dangi.js b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-dangi.js
new file mode 100644
index 0000000000..ab28a6b763
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/leap-months-dangi.js
@@ -0,0 +1,126 @@
+// Copyright (C) 2025 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-temporal.zoneddatetime.prototype.subtract
+description: Arithmetic around leap months in the dangi calendar
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "dangi";
+const options = { overflow: "reject" };
+
+// Years
+
+const years1 = new Temporal.Duration(-1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2019, monthCode: "M01", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  2020, 1, "M01", 1, 12, 34, 0, 0, 0, 0, "add 1 year from non-leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1966, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  1967, 3, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 year from leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1938, monthCode: "M07L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(years1).toPlainDateTime(),
+  1939, 7, "M07", 29, 12, 34, 0, 0, 0, 0, "add 1 year from leap day in leap month"
+);
+
+// Months
+
+const months1 = new Temporal.Duration(0, -1);
+const months1n = new Temporal.Duration(0, 1);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1).toPlainDateTime(),
+  1947, 4, "M03", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1).toPlainDateTime(),
+  1955, 5, "M04", 1, 12, 34, 0, 0, 0, 0, "add 1 month, starting at start of leap month with 30 days"
+);
+
+const date1 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M03", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(months1).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "adding 1 month to M03 in leap year lands in M04 (not M04L)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "adding 2 months to M03 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(new Temporal.Duration(0, -3)).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "adding 3 months to M03 in leap year lands in M05 (not M06)"
+);
+
+const date2 = Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M06", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(months1n).toPlainDateTime(),
+  2020, 6, "M05", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M06 in leap year lands in M05"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 2)).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 2 months from M06 in leap year lands in M04L (leap month)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(new Temporal.Duration(0, 3)).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 3 months from M06 in leap year lands in M04 (not M03)"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M05", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1n).toPlainDateTime(),
+  2020, 5, "M04L", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M05 in leap year lands in M04L"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 2020, monthCode: "M04L", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months1n).toPlainDateTime(),
+  2020, 4, "M04", 1, 12, 34, 0, 0, 0, 0, "Subtracting 1 month from M04L in calendar lands in M04"
+);
+
+// Weeks
+
+const months2weeks3 = new Temporal.Duration(0, /* months = */ -2, /* weeks = */ -3);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1947, 6, "M05", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from last day leap month without leap day"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1955, 7, "M06", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M01", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1947, 4, "M03", 21, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M06", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(months2weeks3).toPlainDateTime(),
+  1955, 10, "M09", 20, 12, 34, 0, 0, 0, 0, "add 2 months 3 weeks from immediately before a leap month"
+);
+
+// Days
+
+const days10 = new Temporal.Duration(0, 0, 0, /* days = */ -10);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1955, monthCode: "M03L", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  1955, 5, "M04", 10, 12, 34, 0, 0, 0, 0, "add 10 days from leap day in leap month"
+);
+
+TemporalHelpers.assertPlainDateTime(
+  Temporal.ZonedDateTime.from({ year: 1947, monthCode: "M02L", day: 29, hour: 12, minute: 34, timeZone: "UTC", calendar }, options).subtract(days10).toPlainDateTime(),
+  1947, 4, "M03", 10, 12, 34, 0, 0, 0, 0, "add 10 days from last day of leap month"
+);