code: function(year, monthIndex) {
          if (year.year) {
              year = year.year();
              monthIndex = year.month();
          }
  
          var intercalaryMonth = this.intercalaryMonth(year);
  
          return !!intercalaryMonth && intercalaryMonth === monthIndex;
      }
docs: Determine whether this date is an intercalary month.
  @memberof ChineseCalendar
  @param year {CDate|number} The date to examine or the year to examine.
  @param [monthIndex] {number} The month index to examine.
  @return {boolean} <code>true</code> if this is an intercalary month, <code>false</code> if not.
  @throws Error if an invalid year or a different calendar used.