diff --git a/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-coptic.js b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-coptic.js
new file mode 100644
index 0000000000..63aeb5b5af
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-coptic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (coptic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "coptic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-coptic.js
+// Months
+
+const common1230 = Temporal.PlainDate.from({ year: 1738, monthCode: "M12", day: 30, calendar }, options);
+const leap1230 = Temporal.PlainDate.from({ year: 1739, monthCode: "M12", day: 30, calendar }, options);
+
+TemporalHelpers.assertPlainDate(
+  common1230.with({ monthCode: "M13" }),
+  1738, 13, "M13", 5, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 1738);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDate(
+  leap1230.with({ monthCode: "M13" }),
+  1739, 13, "M13", 6, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 1739);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethioaa.js b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethioaa.js
new file mode 100644
index 0000000000..8e5fcf49f8
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethioaa.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethioaa calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethioaa";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethioaa.js
+// Months
+
+const common1230 = Temporal.PlainDate.from({ year: 7514, monthCode: "M12", day: 30, calendar }, options);
+const leap1230 = Temporal.PlainDate.from({ year: 7515, monthCode: "M12", day: 30, calendar }, options);
+
+TemporalHelpers.assertPlainDate(
+  common1230.with({ monthCode: "M13" }),
+  7514, 13, "M13", 5, "Changing month constrains to day 5 of common-year epagomenal month",
+  "aa", 7514);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDate(
+  leap1230.with({ monthCode: "M13" }),
+  7515, 13, "M13", 6, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "aa", 7515);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethiopic.js b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethiopic.js
new file mode 100644
index 0000000000..c18dc4cc1e
--- /dev/null
+++ b/test/intl402/Temporal/PlainDate/prototype/with/constrain-day-ethiopic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethiopic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethiopic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethiopic.js
+// Months
+
+const common1230 = Temporal.PlainDate.from({ year: 2014, monthCode: "M12", day: 30, calendar }, options);
+const leap1230 = Temporal.PlainDate.from({ year: 2015, monthCode: "M12", day: 30, calendar }, options);
+
+TemporalHelpers.assertPlainDate(
+  common1230.with({ monthCode: "M13" }),
+  2014, 13, "M13", 5, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 2014);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDate(
+  leap1230.with({ monthCode: "M13" }),
+  2015, 13, "M13", 6, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 2015);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-coptic.js b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-coptic.js
new file mode 100644
index 0000000000..1ff0412c21
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-coptic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (coptic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "coptic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-coptic.js
+// Months
+
+const common1230 = Temporal.PlainDateTime.from({ year: 1738, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+const leap1230 = Temporal.PlainDateTime.from({ year: 1739, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }),
+  1738, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 1738);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }),
+  1739, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 1739);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethioaa.js b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethioaa.js
new file mode 100644
index 0000000000..40f1734ccb
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethioaa.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethioaa calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethioaa";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethioaa.js
+// Months
+
+const common1230 = Temporal.PlainDateTime.from({ year: 7514, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+const leap1230 = Temporal.PlainDateTime.from({ year: 7515, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }),
+  7514, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "aa", 7514);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }),
+  7515, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "aa", 7515);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethiopic.js b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethiopic.js
new file mode 100644
index 0000000000..42640127db
--- /dev/null
+++ b/test/intl402/Temporal/PlainDateTime/prototype/with/constrain-day-ethiopic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethiopic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethiopic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethiopic.js
+// Months
+
+const common1230 = Temporal.PlainDateTime.from({ year: 2014, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+const leap1230 = Temporal.PlainDateTime.from({ year: 2015, monthCode: "M12", day: 30, hour: 12, minute: 34, calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }),
+  2014, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 2014);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }),
+  2015, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 2015);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-coptic.js b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-coptic.js
new file mode 100644
index 0000000000..a0a4296897
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-coptic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (coptic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "coptic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-coptic.js
+// Months
+
+const common1230 = Temporal.ZonedDateTime.from({ year: 1738, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+const leap1230 = Temporal.ZonedDateTime.from({ year: 1739, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  1738, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 1738);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  1739, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 1739);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethioaa.js b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethioaa.js
new file mode 100644
index 0000000000..a8aaa6e75d
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethioaa.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethioaa calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethioaa";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethioaa.js
+// Months
+
+const common1230 = Temporal.ZonedDateTime.from({ year: 7514, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+const leap1230 = Temporal.ZonedDateTime.from({ year: 7515, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  7514, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "aa", 7514);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  7515, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "aa", 7515);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");
diff --git a/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethiopic.js b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethiopic.js
new file mode 100644
index 0000000000..3b31e3bb84
--- /dev/null
+++ b/test/intl402/Temporal/ZonedDateTime/prototype/with/constrain-day-ethiopic.js
@@ -0,0 +1,36 @@
+// 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.with
+description: >
+  Check various basic calculations involving constraining days to the end of the
+  epagomenal month (ethiopic calendar)
+features: [Temporal, Intl.Era-monthcode]
+includes: [temporalHelpers.js]
+---*/
+
+const calendar = "ethiopic";
+const options = { overflow: "reject" };
+
+// Years - see leap-year-ethiopic.js
+// Months
+
+const common1230 = Temporal.ZonedDateTime.from({ year: 2014, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+const leap1230 = Temporal.ZonedDateTime.from({ year: 2015, monthCode: "M12", day: 30, hour: 12, minute: 34, timeZone: "UTC", calendar }, options);
+
+TemporalHelpers.assertPlainDateTime(
+  common1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  2014, 13, "M13", 5, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 5 of common-year epagomenal month",
+  "am", 2014);
+assert.throws(RangeError, function () {
+  common1230.with({ monthCode: "M13" }, options);
+}, "Changing month to common-year epagomenal month rejects");
+
+TemporalHelpers.assertPlainDateTime(
+  leap1230.with({ monthCode: "M13" }).toPlainDateTime(),
+  2015, 13, "M13", 6, 12, 34, 0, 0, 0, 0, "Changing month constrains to day 6 of leap-year epagomenal month",
+  "am", 2015);
+assert.throws(RangeError, function () {
+  leap1230.with({ monthCode: "M13" }, options);
+}, "Changing month to leap-year epagomenal month rejects");