code: public GeneralTimestamp<C> plus(CalendarDays days) {
  
          CalendarVariant<?> ncv = (this.cv == null) ? null : this.cv.plus(days);
          Calendrical<?, ?> nca = (this.ca == null) ? null : this.ca.plus(days);
          return new GeneralTimestamp<>(ncv, nca, this.time);
  
      }
docs: /*[deutsch]
  <p>F&uuml;gt die angegebene Anzahl von Tagen zu diesem allgemeinen Zeitstempel hinzu
  und liefert das Additionsergebnis. </p>
  
  @param   days    the duration in days to be added
  @return  result of addition as changed copy, this instance remains unaffected
  @throws  ArithmeticException in case of numerical overflow
  @since   5.0