1 files changed, 30 insertions, 0 deletions
diff --git a/js/src/tests/non262/Date/reset-time-zone-cache-same-offset.js b/js/src/tests/non262/Date/reset-time-zone-cache-same-offset.js
new file mode 100644
index 0000000000..56c9fc262c
--- /dev/null
+++ b/js/src/tests/non262/Date/reset-time-zone-cache-same-offset.js
@@ -0,0 +1,30 @@
+// |reftest| skip-if(xulRuntime.OS=="WINNT") -- Windows doesn't accept IANA names for the TZ env variable
+
+const testCases = [
+    {
+        timeZone: "Europe/London",
+        string: "Tue Aug 14 2018 00:00:00 GMT+0100 (BST)",
+        alternativeTimeZones: ["British Summer Time"],
+        localeString: "8/14/2018, 12:00:00 AM GMT+1",
+    },
+    {
+        timeZone: "UTC",
+        string: "Tue Aug 14 2018 00:00:00 GMT+0000 (UTC)",
+        alternativeTimeZones: ["Coordinated Universal Time"],
+        localeString: "8/14/2018, 12:00:00 AM UTC",
+    },
+];
+
+// Repeat twice to test both transitions (Europe/London -> UTC and UTC -> Europe/London).
+for (let i = 0; i < 2; ++i) {
+    for (let {timeZone, string, localeString, alternativeTimeZones} of testCases) {
+        setTimeZone(timeZone);
+
+        let dt = new Date(2018, 8 - 1, 14);
+        assertDateTime(dt, string, ...alternativeTimeZones);
+        assertEq(dt.toLocaleString("en-US", {timeZoneName: "short"}), localeString);
+    }
+}
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);