Temporal: Add tests covering one operand of ZonedDateTime difference at extreme

These tests cover the case where the ZonedDateTime since() or until()
methods are called with either the receiver or the argument being a
ZonedDateTime instance at either the earliest or latest end of the
supported range.

test/built-ins/Temporal/ZonedDateTime/prototype/since/argument-at-limits.js

@@ -0,0 +1,43 @@
+// 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.since
+description: One of the operands is at the limit of the supported epoch ns range
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const max = new Temporal.ZonedDateTime(86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["UTC", "+02:00", "-07:00"]) {
+  const limit = max.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 1, 1, 1, 1, 1, 1, 1, 1).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.since(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.since(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic since limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}
+
+const min = new Temporal.ZonedDateTime(-86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["UTC", "+00:18", "-08:12"]) {
+  const limit = min.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 9, 1, 15, 47, 32).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.since(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.since(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic since limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}

test/built-ins/Temporal/ZonedDateTime/prototype/until/argument-at-limits.js

@@ -0,0 +1,43 @@
+// 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.until
+description: One of the operands is at the limit of the supported epoch ns range
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const max = new Temporal.ZonedDateTime(86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["UTC", "+02:00", "-07:00"]) {
+  const limit = max.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 1, 1, 1, 1, 1, 1, 1, 1).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.until(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.until(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic until limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}
+
+const min = new Temporal.ZonedDateTime(-86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["UTC", "+00:18", "-08:12"]) {
+  const limit = min.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 9, 1, 15, 47, 32).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.until(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.until(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic until limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}

test/intl402/Temporal/ZonedDateTime/prototype/since/argument-at-limits.js

@@ -0,0 +1,43 @@
+// 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.since
+description: One of the operands is at the limit of the supported epoch ns range
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const max = new Temporal.ZonedDateTime(86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["Etc/GMT+0", "Europe/Amsterdam", "America/Vancouver"]) {
+  const limit = max.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 1, 1, 1, 1, 1, 1, 1, 1).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.since(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.since(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic since limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}
+
+const min = new Temporal.ZonedDateTime(-86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["Etc/GMT+0", "Europe/Amsterdam", "America/Vancouver"]) {
+  const limit = min.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 9, 1, 15, 47, 32).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.since(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.since(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic since limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}

test/intl402/Temporal/ZonedDateTime/prototype/until/argument-at-limits.js

@@ -0,0 +1,43 @@
+// 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.until
+description: One of the operands is at the limit of the supported epoch ns range
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+const max = new Temporal.ZonedDateTime(86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["Etc/GMT+0", "Europe/Amsterdam", "America/Vancouver"]) {
+  const limit = max.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 1, 1, 1, 1, 1, 1, 1, 1).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.until(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.until(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic until limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}
+
+const min = new Temporal.ZonedDateTime(-86400_0000_0000_000_000_000n, "UTC");
+
+for (const timeZone of ["Etc/GMT+0", "Europe/Amsterdam", "America/Vancouver"]) {
+  const limit = min.withTimeZone(timeZone);
+  const instance = new Temporal.PlainDateTime(1970, 9, 1, 15, 47, 32).toZonedDateTime(timeZone);
+
+  instance.since(limit, { largestUnit: "years" });  // should not throw
+  limit.since(instance, { largestUnit: "years" });  // should not throw
+
+  const resultTimeUnit = instance.until(limit, { largestUnit: "seconds" });
+  TemporalHelpers.assertDurationsEqual(
+    limit.until(instance, { largestUnit: "seconds" }),
+    resultTimeUnit.negated(),
+    `Arithmetic until limit with time largestUnit is self-consistent (${timeZone})`
+  );
+}