code: def datetime_to_dtstr(dt=None):
      
      if dt is None:
          dt = datetime.datetime.utcnow()
      elif timezone.is_aware(dt):
          dt = dt.astimezone(tz=pytz.UTC)
      return int2base36(int(time.mktime(dt.timetuple()) * 1e3 + dt.microsecond / 1e3))
docs: Comvert datetime to short text.
      If datetime has timezone then it will be convert to UTC0.