Make most arguments to Date constructor optional.

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) {
     if (!(other is TimeZoneImplementation)) return false;
     return isUtc == other.isUtc;
   }
 
   final bool isUtc;
 }
 
 // JavaScript implementation of DateImplementation.
 class DateImplementation implements Date {
   factory DateImplementation(int years,
-                             int month,
-                             int day,
-                             int hours,
-                             int minutes,
-                             int seconds,
-                             int milliseconds) {
+                             [int month = 1,
+                              int day = 1,
+                              int hours = 0,
+                              int minutes = 0,
+                              int seconds = 0,
+                              int milliseconds = 0]) {
     return new DateImplementation.withTimeZone(
         years, month, day,
         hours, minutes, seconds, milliseconds,
         new TimeZoneImplementation.local());
   }
 
   DateImplementation.withTimeZone(int years,
                                   int month,
                                   int day,
                                   int hours,
@@ skipping 369 matching lines @@
 
   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";
 }