code: def date_range(data):
      
      start = min([parse(d['activity_start_time']) for d in data])
      end = max([parse(d['activity_end_time']) for d in data])
      start = remove_hours(start)
      end = remove_hours(end) + timedelta(days=1)
      return start, end
docs: Returns the minimum activity start time and the maximum activity end time
      from the active entities response. These dates are modified in the following
      way. The hours (and minutes and so on) are removed from the start and end
      times and a *day* is added to the end time. These are the dates that should
      be used in the subsequent analytics request.