From d90b7b6714f3bb195950108005a8ff8cfc0d667f Mon Sep 17 00:00:00 2001
From: Jordan Harband <ljharb@gmail.com>
Date: Wed, 24 Feb 2016 01:45:38 -0800
Subject: [PATCH] [Fix] `new Date(new Date())` should work in IE 8.

Fixes #389.
---
 es5-shim.js          | 2 +-
 tests/spec/s-date.js | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/es5-shim.js b/es5-shim.js
index f8d8878c..d9d87d65 100644
--- a/es5-shim.js
+++ b/es5-shim.js
@@ -1418,7 +1418,7 @@ if (doesNotParseY2KNewYear || acceptsInvalidDates || !supportsExtendedYears) {
                     length >= 4 ? new NativeDate(Y, M, D, h) :
                     length >= 3 ? new NativeDate(Y, M, D) :
                     length >= 2 ? new NativeDate(Y, M) :
-                    length >= 1 ? new NativeDate(Y) :
+                    length >= 1 ? new NativeDate(Y instanceof NativeDate ? +Y : Y) :
                                   new NativeDate();
             } else {
                 date = NativeDate.apply(this, arguments);
diff --git a/tests/spec/s-date.js b/tests/spec/s-date.js
index e46a1946..1684926a 100644
--- a/tests/spec/s-date.js
+++ b/tests/spec/s-date.js
@@ -167,6 +167,15 @@ describe('Date', function () {
             var expectedVeryBrokenTS = veryBrokenTS + (largeDate.getTimezoneOffset() * 60e3);
             expect(veryBrokenDate.getTime()).toBe(expectedVeryBrokenTS); // NaN in Safari 8/9
         });
+
+        it('works with a Date object', function () {
+            var date = new Date(1456297712984);
+            var copiedDate = new Date(date);
+            expect(date).not.toBe(copiedDate);
+            expect(copiedDate.getTime()).toBe(date.getTime());
+            expect(+copiedDate).toBe(+date);
+            expect(String(copiedDate)).toBe(String(date));
+        });
     });
 
     describe('.parse()', function () {