def month_delta(date, delta):

    """Function:  month_delta

    Description:  Produces a month delta based on date passed to function.

    Arguments:
        (input) date -> Date time.
        (input) delta -> Delta on date time (i.e. -n...0...n).
        (output) month = Numeric month of the year.
        (outout) year = Numeric year in 4-digit format.

    """

    month, year = \
        (date.month + delta) % 12, date.year + ((date.month) + delta - 1) // 12

    if not month:
        month = 12

    return month, year