diff --git a/implementation-contributed/javascriptcore/stress/date-utc-optional.js b/implementation-contributed/javascriptcore/stress/date-utc-optional.js
new file mode 100644
index 0000000000..f14f7c60c6
--- /dev/null
+++ b/implementation-contributed/javascriptcore/stress/date-utc-optional.js
@@ -0,0 +1,16 @@
+function shouldBe(actual, expected) {
+    if (actual !== expected)
+        throw new Error('bad value: ' + actual);
+}
+
+for (var i = 0; i < 1e5; ++i) {
+    shouldBe(Number.isNaN(Date.UTC()), true);
+    shouldBe(Date.UTC(2018), 1514764800000);
+    shouldBe(Date.UTC(2018, 1), 1517443200000);
+    shouldBe(Date.UTC(2018, 1, 2), 1517529600000);
+    shouldBe(Date.UTC(2018, 1, 2, 3), 1517540400000);
+    shouldBe(Date.UTC(2018, 1, 2, 3, 4), 1517540640000);
+    shouldBe(Date.UTC(2018, 1, 2, 3, 4, 5), 1517540645000);
+    shouldBe(Date.UTC(2018, 1, 2, 3, 4, 5, 6), 1517540645006);
+    shouldBe(Date.UTC(2018, 1, 2, 3, 4, 5, 6, 7), 1517540645006);
+}