code: public D minus(CalendarDays days) {
  
          return this.plus(CalendarDays.of(Math.negateExact(days.getAmount())));
  
      }
docs: /*[deutsch]
  <p>Subtrahiert die angegebenen Kalendertage von dieser Instanz. </p>
  
  @param   days    calendar days to be subtracted
  @return  result of subtraction
  @throws  ArithmeticException in case of numerical overflow
  @since   3.4/4.3