code: protected int handleGetMonthLength(int extendedYear, int month) {
          return handleComputeMonthStart(extendedYear, month+1, true) -
                  handleComputeMonthStart(extendedYear, month, true);
      }
docs: Returns the number of days in the given month of the given extended
  year of this calendar system.  Subclasses should override this
  method if they can provide a more correct or more efficient
  implementation than the default implementation in Calendar.