code: int getDaysInMonthMax(long instant) {
          int thisYear = getYear(instant);
          int thisMonth = getMonthOfYear(instant, thisYear);
          return getDaysInYearMonth(thisYear, thisMonth);
      }
docs: Gets the maximum number of days in the month specified by the instant.
  
  @param instant  millis from 1970-01-01T00:00:00Z
  @return the maximum number of days in the month