code: function(year, monthIndex) {
              if (year.year) {
                  monthIndex = year.month();
                  year = year.year();
              }
  
              year = this._validateYear(year);
  
              var monthDaysTable = LUNAR_MONTH_DAYS[year - LUNAR_MONTH_DAYS[0]];
  
              var intercalaryMonth = monthDaysTable >> 13;
              var maxMonthIndex = (intercalaryMonth) ? 12 : 11;
              if (monthIndex > maxMonthIndex) {
                  throw $.calendars.local.invalidMonth
                      .replace(/\{0\}/, this.local.name);
              }
  
              var daysInMonth = (monthDaysTable & (1 << (12 - monthIndex))) ?
                  30 : 29;
  
              return daysInMonth;
          }
docs: Retrieve the number of days in a month.
  @memberof ChineseCalendar
  @param year {CDate|number} The date to examine or the year of the month.
  @param [monthIndex] {number} The month index.
  @return {number} The number of days in this month.
  @throws Error if an invalid month/year or a different calendar used.