code: function () {
              var year = this.get(YEAR);    // implicitly  complete
              // implicitly  complete
              var weekOfYear = this.get(WEEK_OF_YEAR);
              var month = this.get(MONTH);
              if (month === GregorianCalendar.JANUARY) {
                  if (weekOfYear >= 52) {
                      --year;
                  }
              } else if (month === GregorianCalendar.DECEMBER) {
                  if (weekOfYear === 1) {
                      ++year;
                  }
              }
              return year;
          }
docs: Returns the week year represented by this GregorianCalendar.
  The dates in the weeks between 1 and the
  maximum week number of the week year have the same week year value
  that may be one year before or after the calendar year value.
  
  @return {Number} the week year represented by this GregorianCalendar.