Add support for timezone offset and timezone name.

runtime/lib/date.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Dart core library.
 
 class TimeZoneImplementation implements TimeZone {
   const TimeZoneImplementation.utc() : isUtc = true;
   TimeZoneImplementation.local() : isUtc = false {}
 
   bool operator ==(Object other) {
@@ skipping 112 matching lines @@
   int compareTo(Date other) => value.compareTo(other.value);
   int hashCode() => value;
 
   Date changeTimeZone(TimeZone targetTimeZone) {
     if (targetTimeZone === null) {
       targetTimeZone = new TimeZoneImplementation.local();
     }
     return new Date.fromEpoch(value, targetTimeZone);
   }
 
+  String get timeZoneName() {
+    if (isUtc()) return "UTC";
+    return _timeZoneName(_equivalentSeconds(_secondsSinceEpoch));
+  }
+
+  Duration get timeZoneOffset() {
+    if (isUtc()) return new Duration(0);
+    int offsetInSeconds =
+        _timeZoneOffsetInSeconds(_equivalentSeconds(_secondsSinceEpoch));
+    return new Duration(seconds: offsetInSeconds);
+  }
+
   int get year() {
     int secondsSinceEpoch = _secondsSinceEpoch;
     // According to V8 some library calls have troubles with negative values.
     // Therefore clamp to 0 - year 2035 (which is less than the size of 32bit).
     if (secondsSinceEpoch >= 0 && secondsSinceEpoch < _SECONDS_YEAR_2035) {
       return _getYear(secondsSinceEpoch, timeZone.isUtc);
     }
 
     // Approximate the result. We don't take timeZone into account.
     int approximateYear = _yearsFromSecondsSinceEpoch(secondsSinceEpoch);
@@ skipping 251 matching lines @@
     return adjustedSeconds * Duration.MILLISECONDS_PER_SECOND + milliseconds;
   }
 
   // Natives
   static _brokenDownDateToSecondsSinceEpoch(
       int years, int month, int day, int hours, int minutes, int seconds,
       bool isUtc) native "DateNatives_brokenDownToSecondsSinceEpoch";
 
   static int _getCurrentMs() native "DateNatives_currentTimeMillis";
 
+  static String _timeZoneName(int secondsSinceEpoch)
+      native "DateNatives_timeZoneName";
+
+  static int _timeZoneOffsetInSeconds(int secondsSinceEpoch)
+      native "DateNatives_timeZoneOffsetInSeconds";
+
   // TODO(floitsch): it would be more efficient if we didn't call the native
   // function for every member, but cached the broken-down date.
   static int _getYear(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getYear";
 
   static int _getMonth(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getMonth";
 
   static int _getDay(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getDay";
 
   static int _getHours(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getHours";
 
   static int _getMinutes(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getMinutes";
 
   static int _getSeconds(int secondsSinceEpoch, bool isUtc)
       native "DateNatives_getSeconds";
 }