code: function(year, month) {
  			var date = this._validate(year, month, this.minDay,
  				$.calendars.local.invalidMonth || $.calendars.regionalOptions[''].invalidMonth);
  			return (date.month() + this.monthsInYear(date) - this.firstMonth) %
  				this.monthsInYear(date) + this.minMonth;
  		}
docs: Calculate the month's ordinal position within the year -
  for those calendars that don't start at month 1!
  @memberof BaseCalendar
  @param year {CDate|number} The date to examine or the year to examine.
  @param month {number} The month to examine.
  @return {number} The ordinal position, starting from <code>minMonth</code>.
  @throws Error if an invalid year/month or a different calendar used.