code: public TimestampInterval toFullDays() {
  
          Boundary<PlainTimestamp> b1;
          Boundary<PlainTimestamp> b2;
  
          if (this.getStart().isInfinite()) {
              b1 = Boundary.infinitePast();
          } else {
              PlainDate d1 = this.getStart().getTemporal();
              PlainTimestamp t1;
              if (this.getStart().isOpen()) {
                  t1 = d1.at(PlainTime.midnightAtEndOfDay());
              } else {
                  t1 = d1.atStartOfDay();
              }
              b1 = Boundary.of(IntervalEdge.CLOSED, t1);
          }
  
          if (this.getEnd().isInfinite()) {
              b2 = Boundary.infiniteFuture();
          } else {
              PlainDate d2 = this.getEnd().getTemporal();
              PlainTimestamp t2;
              if (this.getEnd().isOpen()) {
                  t2 = d2.atStartOfDay();
              } else {
                  t2 = d2.at(PlainTime.midnightAtEndOfDay());
              }
              b2 = Boundary.of(IntervalEdge.OPEN, t2);
          }
  
          return new TimestampInterval(b1, b2);
  
      }
docs: /*[deutsch]
  <p>Wandelt diese Instanz in ein Zeitstempelintervall
  mit Datumswerten von Mitternacht zu Mitternacht um. </p>
  
  <p>Das Ergebnisintervall ist halb-offen, wenn dieses Intervall
  endlich ist. </p>
  
  @return  timestamp interval (from midnight to midnight)
  @since   2.0