code: public boolean equalsDurationInMilliseconds(Timespan timespan) {
          // shortcut when time unit are the same
          if (timespan.getTimeUnit() == getTimeUnit()) {
              return timespan.getDuration() == getDuration();
          } else {
              return getDurationInMilliseconds() == timespan.getDurationInMilliseconds();
          }
      }
docs: 2 timespans can be different (1h and 3600s) while representing the same duration expressed
  in milliseconds... This method tests for this.
  
  @param timespan
  the other timespan to compare with
  
  @return <code>true</code> if this timespan and the provided one represent the same
  duration of time.