code: protected int getDefaultDayInMonth(int extendedYear, int month) {
        int era = internalGet(ERA, CURRENT_ERA);
            
        if(extendedYear == ERAS[era*3]) { // if it is year 1..
          if(month == ((ERAS[(era*3)+1])-1)) { // if it is the emperor's first month.. 
            return ERAS[(era*3)+2]; // return the D_O_M of acession
          }
        }
  
        return super.getDefaultDayInMonth(extendedYear, month);
      }
docs: Called by handleComputeJulianDay.  Returns the default day (1-based) for the month,
  taking currently-set year and era into account.  Defaults to 1 for Gregorian.
  @param extendedYear the extendedYear, as returned by handleGetExtendedYear
  @param month the month, as returned by getDefaultMonthInYear
  @return the default day of the month
  @see #DAY_OF_MONTH
  @hide draft / provisional / internal are hidden on Android