code: public Moment in(Timezone tz) {
  
          if (tz.isFixed()) { // optimization
              return this.at(tz.getOffset(this.date, this.time));
          }
  
          TransitionStrategy strategy = tz.getStrategy();
          long posixTime = strategy.resolve(this.date, this.time, tz);
          Moment moment =
              Moment.of(posixTime, this.time.getNanosecond(), TimeScale.POSIX);
  
          if (strategy == Timezone.STRICT_MODE) {
              Moment.checkNegativeLS(posixTime, this);
          }
  
          return moment;
  
      }
docs: /*[deutsch]
  <p>Kombiniert diesen lokalen Zeitstempel mit der angegebenen Zeitzone
  zu einem UTC-Moment. </p>
  
  @param   tz      timezone
  @return  global UTC-moment based on this local timestamp interpreted
  in given timezone
  @since   1.2
  @see     Timezone#of(String)