Make most arguments to Date constructor optional.

frog/lib/date_implementation.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.
 
 // TODO(jmesserly): the native class should be the real JS Date.
 // TODO(jimhug): Making the date value non-lazy might be a good path there.
 class DateImplementation implements Date {
   final int value;
   final TimeZone timeZone;
 
   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 247 matching lines @@
     return isUtc == other.isUtc;
   }
 
   String toString() {
     if (isUtc) return "TimeZone (UTC)";
     return "TimeZone (Local)";
   }
 
   final bool isUtc;
 }