code: public CalendarDays minus(CalendarDays other) {
  
          return CalendarDays.of(Math.subtractExact(this.days, other.days));
  
      }
docs: /*[deutsch]
  <p>Liefert die Differenz der Kalendertage dieser Instanz und des angegebenen Arguments. </p>
  
  @param   other   calendar days to be subtracted
  @return  delta of calendar days
  @since   3.4/4.3