diff --git a/test/intl402/Temporal/PlainDate/prototype/add/era-boundary-japanese.js b/test/intl402/Temporal/PlainDate/prototype/add/era-boundary-japanese.js
new file mode 100644
index 0000000000..9513d37fc1
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/add/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(1);
+const duration1n = new Temporal.Duration(-1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.PlainDate.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.add(duration1),
+  2019, 3, "M03", 15, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.PlainDate.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.add(duration1),
+  2020, 4, "M04", 15, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.PlainDate.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date3.add(duration1),
+  2019, 6, "M06", 12, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date4.add(duration1),
+  2020, 6, "M06", 10, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.PlainDate.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date5.add(new Temporal.Duration(3)),
+  2019, 7, "M07", 1, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date6.add(duration1n),
+  2019, 6, "M06", 15, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date7.add(duration1n),
+  2019, 3, "M03", 15, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date8.add(duration1n),
+  2018, 7, "M07", 10, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date9.add(new Temporal.Duration(-5)),
+  2017, 2, "M02", 1, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);
diff --git a/test/intl402/Temporal/PlainDate/prototype/subtract/era-boundary-japanese.js b/test/intl402/Temporal/PlainDate/prototype/subtract/era-boundary-japanese.js
new file mode 100644
index 0000000000..301d7d1d1c
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/subtract/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(-1);
+const duration1n = new Temporal.Duration(1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.PlainDate.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date1.subtract(duration1),
+  2019, 3, "M03", 15, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.PlainDate.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date2.subtract(duration1),
+  2020, 4, "M04", 15, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.PlainDate.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date3.subtract(duration1),
+  2019, 6, "M06", 12, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date4.subtract(duration1),
+  2020, 6, "M06", 10, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.PlainDate.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date5.subtract(new Temporal.Duration(-3)),
+  2019, 7, "M07", 1, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date6.subtract(duration1n),
+  2019, 6, "M06", 15, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date7.subtract(duration1n),
+  2019, 3, "M03", 15, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date8.subtract(duration1n),
+  2018, 7, "M07", 10, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.PlainDate.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, calendar }, options);
+TemporalHelpers.assertPlainDate(
+  date9.subtract(new Temporal.Duration(5)),
+  2017, 2, "M02", 1, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/add/era-boundary-japanese.js b/test/intl402/Temporal/PlainDateTime/prototype/add/era-boundary-japanese.js
new file mode 100644
index 0000000000..1922d6bf55
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/add/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(1);
+const duration1n = new Temporal.Duration(-1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(duration1),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(duration1),
+  2020, 4, "M04", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date3.add(duration1),
+  2019, 6, "M06", 12, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date4.add(duration1),
+  2020, 6, "M06", 10, 12, 34, 0, 0, 0, 0, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date5.add(new Temporal.Duration(3)),
+  2019, 7, "M07", 1, 12, 34, 0, 0, 0, 0, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date6.add(duration1n),
+  2019, 6, "M06", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date7.add(duration1n),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date8.add(duration1n),
+  2018, 7, "M07", 10, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date9.add(new Temporal.Duration(-5)),
+  2017, 2, "M02", 1, 12, 34, 0, 0, 0, 0, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/subtract/era-boundary-japanese.js b/test/intl402/Temporal/PlainDateTime/prototype/subtract/era-boundary-japanese.js
new file mode 100644
index 0000000000..ee13d1a5c3
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/subtract/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(-1);
+const duration1n = new Temporal.Duration(1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(duration1),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(duration1),
+  2020, 4, "M04", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date3.subtract(duration1),
+  2019, 6, "M06", 12, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date4.subtract(duration1),
+  2020, 6, "M06", 10, 12, 34, 0, 0, 0, 0, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.PlainDateTime.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date5.subtract(new Temporal.Duration(-3)),
+  2019, 7, "M07", 1, 12, 34, 0, 0, 0, 0, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date6.subtract(duration1n),
+  2019, 6, "M06", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date7.subtract(duration1n),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date8.subtract(duration1n),
+  2018, 7, "M07", 10, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.PlainDateTime.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, hour: 12, minute: 34, calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date9.subtract(new Temporal.Duration(5)),
+  2017, 2, "M02", 1, 12, 34, 0, 0, 0, 0, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/add/era-boundary-japanese.js b/test/intl402/Temporal/ZonedDateTime/prototype/add/era-boundary-japanese.js
new file mode 100644
index 0000000000..1ba8e2ea4a
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/add/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(1);
+const duration1n = new Temporal.Duration(-1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.add(duration1).toPlainDateTime(),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.add(duration1).toPlainDateTime(),
+  2020, 4, "M04", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date3.add(duration1).toPlainDateTime(),
+  2019, 6, "M06", 12, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date4.add(duration1).toPlainDateTime(),
+  2020, 6, "M06", 10, 12, 34, 0, 0, 0, 0, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date5.add(new Temporal.Duration(3)).toPlainDateTime(),
+  2019, 7, "M07", 1, 12, 34, 0, 0, 0, 0, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date6.add(duration1n).toPlainDateTime(),
+  2019, 6, "M06", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date7.add(duration1n).toPlainDateTime(),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date8.add(duration1n).toPlainDateTime(),
+  2018, 7, "M07", 10, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date9.add(new Temporal.Duration(-5)).toPlainDateTime(),
+  2017, 2, "M02", 1, 12, 34, 0, 0, 0, 0, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/subtract/era-boundary-japanese.js b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/era-boundary-japanese.js
new file mode 100644
index 0000000000..96431233d3
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/subtract/era-boundary-japanese.js
@@ -0,0 +1,81 @@
+// 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: >
+  Adding years works correctly across era boundaries in calendars with eras
+includes: [temporalHelpers.js]
+features: [Temporal, Intl.Era-monthcode]
+---*/
+
+// Reiwa era started on May 1, 2019 (Reiwa 1 = 2019)
+// Heisei era: 1989-2019 (Heisei 31 ended April 30, 2019)
+
+const duration1 = new Temporal.Duration(-1);
+const duration1n = new Temporal.Duration(1);
+const calendar = "japanese";
+const options = { overflow: "reject" };
+
+const date1 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M03", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date1.subtract(duration1).toPlainDateTime(),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 March (before May 1) lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date2 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 31, monthCode: "M04", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date2.subtract(duration1).toPlainDateTime(),
+  2020, 4, "M04", 15, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 31 April (before May 1) lands in Reiwa 2 April",
+  "reiwa", 2
+);
+
+const date3 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 30, monthCode: "M06", day: 12, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date3.subtract(duration1).toPlainDateTime(),
+  2019, 6, "M06", 12, 12, 34, 0, 0, 0, 0, "Adding 1 year to Heisei 30 June (after May 1) lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date4 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M06", day: 10, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date4.subtract(duration1).toPlainDateTime(),
+  2020, 6, "M06", 10, 12, 34, 0, 0, 0, 0, "Adding 1 year to Reiwa 1 June lands in Reiwa 2 June",
+  "reiwa", 2
+);
+
+const date5 = Temporal.ZonedDateTime.from({ era: "heisei", eraYear: 28, monthCode: "M07", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date5.subtract(new Temporal.Duration(-3)).toPlainDateTime(),
+  2019, 7, "M07", 1, 12, 34, 0, 0, 0, 0, "Multiple years across era boundary: Adding 3 years to Heisei 28 July lands in Reiwa 1 July",
+  "reiwa", 1
+);
+
+const date6 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M06", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date6.subtract(duration1n).toPlainDateTime(),
+  2019, 6, "M06", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 June lands in Reiwa 1 June",
+  "reiwa", 1
+);
+
+const date7 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 2, monthCode: "M03", day: 15, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date7.subtract(duration1n).toPlainDateTime(),
+  2019, 3, "M03", 15, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 2 March lands in Heisei 31 March",
+  "heisei", 31
+);
+
+const date8 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 1, monthCode: "M07", day: 10, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date8.subtract(duration1n).toPlainDateTime(),
+  2018, 7, "M07", 10, 12, 34, 0, 0, 0, 0, "Subtracting 1 year from Reiwa 1 July lands in Heisei 30 July",
+  "heisei", 30
+);
+
+const date9 = Temporal.ZonedDateTime.from({ era: "reiwa", eraYear: 4, monthCode: "M02", day: 1, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+TemporalHelpers.assertPlainDateTime(
+  date9.subtract(new Temporal.Duration(5)).toPlainDateTime(),
+  2017, 2, "M02", 1, 12, 34, 0, 0, 0, 0, "Subtracting 5 years from Reiwa 4 February lands in Heisei 29 February",
+  "heisei", 29
+);