Fix printing of dates with year 0.

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.
 
 // VM implementation of DateImplementation.
 class DateImplementation implements Date {
   static final int _MAX_MILLISECONDS_SINCE_EPOCH = 8640000000000000;
 
   DateImplementation(int years,
@@ skipping 178 matching lines @@
         Date.MON;
   }
 
   String toString() {
     String fourDigits(int n) {
       int absN = n.abs();
       String sign = n < 0 ? "-" : "";
       if (absN >= 1000) return "$n";
       if (absN >= 100) return "${sign}0$absN";
       if (absN >= 10) return "${sign}00$absN";
-      if (absN >= 1) return "${sign}000$absN";
+      return "${sign}000$absN";
     }
     String threeDigits(int n) {
       if (n >= 100) return "${n}";
       if (n >= 10) return "0${n}";
       return "00${n}";
     }
     String twoDigits(int n) {
       if (n >= 10) return "${n}";
       return "0${n}";
     }
@@ skipping 273 matching lines @@
 
   static String _timeZoneNameForClampedSeconds(int secondsSinceEpoch)
       native "DateNatives_timeZoneName";
 
   static int _timeZoneOffsetInSecondsForClampedSeconds(int secondsSinceEpoch)
       native "DateNatives_timeZoneOffsetInSeconds";
 
   static int _localTimeZoneAdjustmentInSeconds()
       native "DateNatives_localTimeZoneAdjustmentInSeconds";
 }