Rename DAYS_IN_WEEK to DAYS_PER_WEEK. Add MONTHS_PER_YEAR.

runtime/lib/date_patch.dart

 // Copyright (c) 2012, 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 DateTime.
 patch class DateTime {
   /* patch */ DateTime._internal(int year,
                                  int month,
                                  int day,
@@ skipping 58 matching lines @@
     return millisecondsSinceEpoch % Duration.MILLISECONDS_PER_SECOND;
   }
 
   /** Returns the weekday of [this]. In accordance with ISO 8601 a week
     * starts with Monday. Monday has the value 1 up to Sunday with 7. */
   /* patch */ int get weekday {
     int daysSince1970 =
         _flooredDivision(_localDateInUtcMs, Duration.MILLISECONDS_PER_DAY);
     // 1970-1-1 was a Thursday.
     return ((daysSince1970 + DateTime.THURSDAY - DateTime.MONDAY)
-            % DateTime.DAYS_IN_WEEK) +
+            % DateTime.DAYS_PER_WEEK) +
         DateTime.MONDAY;
   }
 
 
   /** The first list contains the days until each month in non-leap years. The
     * second list contains the days in leap years. */
   static const List<List<int>> _DAYS_UNTIL_MONTH =
       const [const [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334],
              const [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335]];
 
@@ skipping 226 matching lines @@
 
   static String _timeZoneNameForClampedSeconds(int secondsSinceEpoch)
       native "DateNatives_timeZoneName";
 
   static int _timeZoneOffsetInSecondsForClampedSeconds(int secondsSinceEpoch)
       native "DateNatives_timeZoneOffsetInSeconds";
 
   static int _localTimeZoneAdjustmentInSeconds()
       native "DateNatives_localTimeZoneAdjustmentInSeconds";
 }