code: public PrettyTime withReferenceClock(TimeSource<?> clock) {
  
          return new PrettyTime(
              this.locale,
              clock,
              this.zeroDigit,
              this.minusSign,
              this.emptyUnit,
              this.weekToDays,
              this.shortStyle,
              this.stdListSeparator,
              this.endListSeparator);
  
      }
docs: /*[deutsch]
  <p>Legt die Bezugszeit f&uuml;r relative Zeitangaben neu fest. </p>
  
  @param   clock   new reference clock
  @return  new instance of {@code PrettyTime} with changed reference clock
  @since   1.2
  @see     #getReferenceClock()
  @see     #printRelative(UnixTime, TZID)
  @see     #printRelative(UnixTime, String)