Update the time zone offset and dst offset when time zone name changes.

src/date.js

 // Copyright 2006-2008 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 570 matching lines @@
 
 
 function TimeString(time) {
   return TwoDigitString(HOUR_FROM_TIME(time)) + ':'
       + TwoDigitString(MIN_FROM_TIME(time)) + ':'
       + TwoDigitString(SEC_FROM_TIME(time));
 }
 
 
 function LocalTimezoneString(time) {
+  var old_timezone = timezone_cache_timezone;
+  var timezone = LocalTimezone(time);
+  if (old_timezone && timezone != old_timezone) {
+    // If the timezone string has changed from the one that we cached,
+    // the local time offset may now be wrong. So we need to update it
+    // and try again.
+    local_time_offset = %DateLocalTimeOffset();
+    // We also need to invalidate the DST cache as the new timezone may have
+    // different DST times.
+    var dst_cache = DST_offset_cache;
+    dst_cache.start = 0;
+    dst_cache.end = -1;
+  }
+
   var timezoneOffset =
       (DaylightSavingsOffset(time) + local_time_offset) / msPerMinute;
   var sign = (timezoneOffset >= 0) ? 1 : -1;
   var hours = FLOOR((sign * timezoneOffset)/60);
   var min   = FLOOR((sign * timezoneOffset)%60);
   var gmt = ' GMT' + ((sign == 1) ? '+' : '-') +
       TwoDigitString(hours) + TwoDigitString(min);
-  return gmt + ' (' +  LocalTimezone(time) + ')';
+  return gmt + ' (' +  timezone + ')';
 }
 
 
 function DatePrintString(time) {
   return DateString(time) + ' ' + TimeString(time);
 }
 
 // -------------------------------------------------------------------
 
 // Reused output buffer. Used when parsing date strings.
@@ skipping 495 matching lines @@
     "toGMTString", DateToGMTString,
     "toUTCString", DateToUTCString,
     "getYear", DateGetYear,
     "setYear", DateSetYear,
     "toISOString", DateToISOString,
     "toJSON", DateToJSON
   ));
 }
 
 SetupDate();