def _get_previous_month(month, year):
    """Returns previous month.

    :param month: Month (integer from 1...12).
    :param year: Year (integer).
    :return: previous_month: Previous month (integer from 1...12).
    :return: previous_year: Previous year (integer).
    """

    previous_month = month - 1

    if previous_month == 0:
        previous_month = 12
        previous_year = year - 1
    else:
        previous_year = year - 0

    return previous_month, previous_year