def date_time(name=None):
    """
    Creates the grammar for a date and time field, which is a combination of
    the Date (D) and Time or Duration field (T).

    This field requires first a Date, and then a Time, without any space in
    between.

    :param name: name for the field
    :return: grammar for a Date and Time field
    """
    if name is None:
        name = 'Date and Time Field'

    date = basic.date('Date')
    time = basic.time('Time')

    date = date.setResultsName('date')
    time = time.setResultsName('time')

    field = pp.Group(date + time)

    field.setParseAction(lambda d: _combine_date_time(d[0]))

    field.setName(name)

    return field.setResultsName('date_time')