anchor.diff:        });
   
     _advanceTo(DateTime to) {
  -    if(to.millisecondsSinceEpoch > _now.millisecondsSinceEpoch) {
  +    if (to.millisecondsSinceEpoch > _now.millisecondsSinceEpoch) {
         _now = to;
       }
     }
  
positive.code:   _runTimer(_FakeTimer timer) {
      assert(timer.isActive);
      _advanceTo(timer._nextCall);
      if(timer._isPeriodic) {
        timer._callback(timer);
        timer._nextCall = timer._nextCall.add(timer._duration);
      } else {
  
negative.code: 
    _scheduleTimer(Zone self, ZoneDelegate parent, Zone zone) {
  
      if (!_waitingForTimer && _advancingTo != null) {
        var next = _getNextTimer();
        var completeTimer = next != null ?
            self.bindCallback(() => _runTimer(next), runGuarded: true) :
  