1 files changed, 28 insertions, 0 deletions
diff --git a/js/src/tests/non262/Intl/DateTimeFormat/formatRange-gregorian-proleptic.js b/js/src/tests/non262/Intl/DateTimeFormat/formatRange-gregorian-proleptic.js
new file mode 100644
index 0000000000..9356577b47
--- /dev/null
+++ b/js/src/tests/non262/Intl/DateTimeFormat/formatRange-gregorian-proleptic.js
@@ -0,0 +1,28 @@
+// |reftest| skip-if(!this.hasOwnProperty("Intl"))
+
+// Ensure formatRange() uses a proleptic Gregorian calendar.
+// ICU bug: https://unicode-org.atlassian.net/browse/ICU-20705
+
+let dtf = new Intl.DateTimeFormat("en", {timeZone: "UTC"});
+
+// The Gregorian calendar was first introduced in 15 October 1582.
+const firstGregorian = new Date("1582-10-15");
+assertEq(dtf.formatRange(firstGregorian, firstGregorian), dtf.format(firstGregorian));
+
+// To deal with the ten days' difference between the Julian and the Gregorian calendar, some days
+// were skipped, so that 4 October 1582 was followed by 15 October 1582.
+const lastJulian = new Date("1582-10-04");
+assertEq(dtf.formatRange(lastJulian, lastJulian), dtf.format(lastJulian));
+
+function rangePart(source, parts) {
+  return parts.filter(x => x.source === source).map(x => x.value).join("");
+}
+
+// Test with non-empty range.
+assertEq(rangePart("startRange", dtf.formatRangeToParts(lastJulian, firstGregorian)),
+         dtf.format(lastJulian));
+assertEq(rangePart("endRange", dtf.formatRangeToParts(lastJulian, firstGregorian)),
+         dtf.format(firstGregorian));
+
+if (typeof reportCompare === "function")
+  reportCompare(0, 0);