code: def _transientSchedule(self, when, now):
          
          if not self.running:
              return
          if self.timer is not None:
              if self.timer.getTime() < when.asPOSIXTimestamp():
                  return
              self.timer.cancel()
          delay = when.asPOSIXTimestamp() - now.asPOSIXTimestamp()
  
          # reactor.callLater allows only positive delay values.  The scheduler
          # may want to have scheduled things in the past and that's OK, since we
          # are dealing with Time() instances it's impossible to predict what
          # they are relative to the current time from user code anyway.
          delay = max(_EPSILON, delay)
          self.timer = self.callLater(delay, self.tick)
          self.nextEventAt = when
docs: If the service is currently running, schedule a tick to happen no
          later than C{when}.
  
          @param when: The time at which to tick.
          @type when: L{epsilon.extime.Time}
  
          @param now: The current time.
          @type now: L{epsilon.extime.Time}