code: function(year, month, day) {
          // Find Monday of this week starting on Monday
          var checkDate = this.newDate(year, month, day);
          checkDate.add(1 - (checkDate.dayOfWeek() || 7), 'd');
          return Math.floor((checkDate.dayOfYear() - 1) / 7) + 1;
      }
docs: Determine the week of the year for a date.
  @memberof NanakshahiCalendar
  @param year {CDate|number} The date to examine or the year to examine.
  @param [month] {number} The month to examine.
  @param [day] {number} The day to examine.
  @return {number} The week of the year.
  @throws Error if an invalid date or a different calendar used.