1 files changed, 48 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/dst-rounding-result.js b/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/dst-rounding-result.js
new file mode 100644
index 0000000000..c3a0f3f3a2
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Temporal/ZonedDateTime/prototype/since/dst-rounding-result.js
@@ -0,0 +1,48 @@
+// |reftest| skip-if(!this.hasOwnProperty('Temporal')) -- Temporal is not enabled unconditionally
+// Copyright (C) 2024 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-temporal.zoneddatetime.prototype.since
+description: >
+    Rounding the resulting duration takes the time zone's UTC offset shifts
+    into account
+includes: [temporalHelpers.js]
+features: [Temporal]
+---*/
+
+// Based on a test case by Adam Shaw
+
+const timeZone = TemporalHelpers.springForwardFallBackTimeZone();
+
+{
+  // Month-only part of duration lands on skipped DST hour, should not cause
+  // disambiguation
+  const start = new Temporal.ZonedDateTime(
+    950868000_000_000_000n /* = 2000-02-18T10Z */,
+    timeZone); /* = 2000-02-18T02-08 in local time */
+  const end = new Temporal.ZonedDateTime(
+    954709200_000_000_000n /* = 2000-04-02T21Z */,
+    timeZone); /* = 2000-04-02T14-07 in local time */
+
+  const duration = start.since(end, { largestUnit: "months" });
+  TemporalHelpers.assertDuration(duration, 0, -1, 0, -15, -11, 0, 0, 0, 0, 0,
+    "1-month rounding window is shortened by DST");
+}
+
+
+{
+  // Month-only part of duration lands on skipped DST hour, should not cause
+  // disambiguation
+  const start = new Temporal.ZonedDateTime(
+    951991200_000_000_000n /* = 2000-03-02T10Z */,
+    timeZone); /* = 2000-03-02T02-08 in local time */
+  const end = new Temporal.ZonedDateTime(
+    956005200_000_000_000n /* = 2000-04-17T21Z */,
+    timeZone); /* = 2000-04-17T14-07 in local time */
+
+  const duration = start.since(end, { largestUnit: "months" });
+  TemporalHelpers.assertDuration(duration, 0, -1, 0, -15, -12, 0, 0, 0, 0, 0,
+    "1-month rounding window is not shortened by DST");
+}
+
+reportCompare(0, 0);