def period_to_month(period, acad_year):
    """
    Financial month and year to calendar month and year.    

    Converts a period and academic year into the actual month number and calendar year.

    Parameters
    ----------
    period : int
        Accounting period
    acad_year : int
        Academic year (calendar year commencing)

    Returns
    -------
    tuple
        Month, Calendar year

    Examples
    --------
    Period 1 (August) in the 2020 financial year:

    >>> period_to_month(1,2020)
    (8, 2020)

    Period 6 (January) in the 1984 financial year: 

    >>> period_to_month(6, 1984)
    (1, 1985)
    """
    # Because August is P1
    period += 7
    # Increment calendar year if new period is in next year (i.e. >12)
    acad_year += (period-1)//12
    # Bring period back to legitimate month number, and correct for 0
    period = period % 12
    if period == 0:
        period = 12
    return period, acad_year