Returns a tuple of all date and time format strings joined together by
  :joiner:.

  :dates: an enumerable of date format strings
  :times: an enumerable of time format strings
  :joiner: a string to join a date and time format together

def _join_date_and_time(dates, times, joiner):
  """Returns a tuple of all date and time format strings joined together by
  :joiner:.

  :dates: an enumerable of date format strings
  :times: an enumerable of time format strings
  :joiner: a string to join a date and time format together
  """
  return tuple("{}{}{}".format(d, joiner, t) for (d, t) in itertools.product(dates, times))