Rename DAYS_IN_WEEK to DAYS_PER_WEEK. Add MONTHS_PER_YEAR.

sdk/lib/core/date_time.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.
 
 part of dart.core;
 
 /**
  * A DateTime object represents a point in time.
  *
  * It can represent time values that are at a distance of at most
  * 8,640,000,000,000,000ms (100,000,000 days) from epoch (1970-01-01 UTC). In
  * other words: [:millisecondsSinceEpoch.abs() <= 8640000000000000:].
  *
  * Also see [Stopwatch] for means to measure time-spans.
  */
 class DateTime {
   // Weekday constants that are returned by [weekday] method:
   static const int MONDAY = 1;
   static const int TUESDAY = 2;
   static const int WEDNESDAY = 3;
   static const int THURSDAY = 4;
   static const int FRIDAY = 5;
   static const int SATURDAY = 6;
   static const int SUNDAY = 7;
-  static const int DAYS_IN_WEEK = 7;
+  static const int DAYS_PER_WEEK = 7;
 
   // Month constants that are returned by the [month] getter.
   static const int JANUARY = 1;
   static const int FEBRUARY = 2;
   static const int MARCH = 3;
   static const int APRIL = 4;
   static const int MAY = 5;
   static const int JUNE = 6;
   static const int JULY = 7;
   static const int AUGUST = 8;
   static const int SEPTEMBER = 9;
   static const int OCTOBER = 10;
   static const int NOVEMBER = 11;
   static const int DECEMBER = 12;
+  static const int MONTHS_PER_YEAR = 12;
 
   /**
    * The milliseconds since 1970-01-01T00:00:00Z (UTC). This value is
    * independent of the time zone.
    *
    * See [Stopwatch] for means to measure time-spans.
    */
   final int millisecondsSinceEpoch;
 
   /**
@@ skipping 320 matching lines @@
    * Returns the millisecond into the second [0...999].
    */
   external int get millisecond;
 
   /**
    * Returns the week day [MON..SUN]. In accordance with ISO 8601
    * a week starts with Monday which has the value 1.
    */
   external int get weekday;
 }