[builtins] Apply ES2016 conditional default timezone semantics

test/mjsunit/date-parse.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 214 matching lines @@
     ['Sat, 01 Jan 99 08:00:00 UT', 915177600000], // year 1999
     ['Sat, 01 Jan 100 08:00:00 UT', -59011430400000], // year 100
     // Test PM after time.
     ['Sat, 01-Jan-2000 08:00 PM UT', 946756800000],
     ['Sat, 01 Jan 2000 08:00 PM UT', 946756800000],
     ['Jan 01 2000 08:00 PM UT', 946756800000],
     ['Jan 01 08:00 PM UT 2000', 946756800000],
     ['Saturday, 01-Jan-00 08:00 PM UT', 946756800000],
     ['01 Jan 00 08:00 PM +0000', 946756800000]];
 
+// TODO(littledan): This is an hack that could break in historically
+// changing timezones that happened on this day, but allows us to
+// check the date value for local times.
+var localOffset = new Date('2000-01-01').getTimezoneOffset()*1000*60;
+
+// Sanity check which is even more of a hack: in the timezones where
+// these tests are likely to be run, the offset is nonzero because
+// dates which don't include Z are in the local timezone.
+if (this.Intl &&
+    ["America/Los_Angeles", "Europe/Berlin", "Europe/Madrid"].indexOf(
+        Intl.DateTimeFormat().resolvedOptions().timeZone) != -1) {
+  assertTrue(localOffset != 0);
+}
+
 // Test different version of the ES5 date time string format.
 var testCasesES5Misc = [
     ['2000-01-01T08:00:00.000Z', 946713600000],
     ['2000-01-01T08:00:00Z', 946713600000],
     ['2000-01-01T08:00Z', 946713600000],
     ['2000-01T08:00:00.000Z', 946713600000],
     ['2000T08:00:00.000Z', 946713600000],
     ['2000T08:00Z', 946713600000],
     ['2000-01T00:00:00.000-08:00', 946713600000],
     ['2000-01T08:00:00.001Z', 946713600001],
     ['2000-01T08:00:00.099Z', 946713600099],
     ['2000-01T08:00:00.999Z', 946713600999],
     ['2000-01T00:00:00.001-08:00', 946713600001],
-    ['2000-01-01T24:00', 946771200000],
-    ['2000-01-01T24:00:00', 946771200000],
-    ['2000-01-01T24:00:00.000', 946771200000],
+    // If the timezone is absent and time is present, use local time

[ulan, 2017/02/15 21:35:04]

The array is named "testCasesES5Misc" but this is testing ES2016 semantics.

Should we rename the array or move these test to separate array?

+    ['2000-01-02T00:00', 946771200000 + localOffset],
+    ['2000-01-02T00:00:00', 946771200000 + localOffset],
+    ['2000-01-02T00:00:00.000', 946771200000 + localOffset],
+    // If timezone is absent and time is absent, use UTC
+    ['2000-01-02', 946771200000],
+    ['2000-01-02', 946771200000],
+    ['2000-01-02', 946771200000],
+    // 24-hour wraparound case
+    ['2000-01-01T24:00Z', 946771200000],
+    ['2000-01-01T24:00:00Z', 946771200000],
+    ['2000-01-01T24:00:00.000Z', 946771200000],
     ['2000-01-01T24:00:00.000Z', 946771200000]];
 
 var testCasesES5MiscNegative = [
     '2000-01-01TZ',
     '2000-01-01T60Z',
     '2000-01-01T60:60Z',
     '2000-01-0108:00Z',
     '2000-01-01T08Z',
     '2000-01-01T24:01',
     '2000-01-01T24:00:01',
@@ skipping 35 matching lines @@
     'May 25 2008 1:30 (PM)) UTC',  // Bad unmatched ')' after number.
     'May 25 2008 1:30( )AM (PM)',  //
     'a1',                          // Issue 126448, 53209.
     'nasfdjklsfjoaifg1',
     'x_2',
     'May 25 2008 AAA (GMT)'];      // Unknown word after number.
 
 testCasesNegative.forEach(function (s) {
     assertTrue(isNaN(Date.parse(s)), s + " is not NaN.");
 });