--- a/js/src/jsdate.h
+++ b/js/src/jsdate.h
@@ -59,17 +59,17 @@ struct JSContext;
 
 namespace js {
 
 /* ES5 15.9.1.14. */
 inline double
 TimeClip(double time)
 {
     /* Steps 1-2. */
-    if (!MOZ_DOUBLE_IS_FINITE(time) || abs(time) > 8.64e15)
+    if (!MOZ_DOUBLE_IS_FINITE(time) || fabs(time) > 8.64e15)
         return js_NaN;
 
     /* Step 3. */
     return ToInteger(time + (+0.0));
 }
 
 } /* namespace js */
 

new file mode 100644
--- /dev/null
+++ b/js/src/tests/ecma_5/Date/timeclip.js
@@ -0,0 +1,42 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommonn.org/licenses/publicdomain/
+ */
+
+var BUGNUMBER = 747197;
+var summary = "TimeClip behavior for very large numbers";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+function addToLimit(n) { return 8.64e15 + n; }
+
+assertEq(8.64e15 === addToLimit(0.0), true);
+assertEq(8.64e15 === addToLimit(0.5), true);
+assertEq(8.64e15 === addToLimit(0.5000000000000001), false);
+
+var times =
+  [Number.MAX_VALUE,
+   -Number.MAX_VALUE,
+   Infinity,
+   -Infinity,
+   addToLimit(0.5000000000000001),
+   -addToLimit(0.5000000000000001)];
+
+for (var i = 0, len = times.length; i < len; i++)
+{
+  var d = new Date();
+  assertEq(d.setTime(times[i]), NaN, "times[" + i + "]");
+  assertEq(d.getTime(), NaN);
+  assertEq(d.valueOf(), NaN);
+}
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("Tests complete");