def yyyymmdd(arrow_date):
    """Return an Arrow date as a string of digits formatted as `yyyymmdd`; e.g. 20020228.

    :param arrow_date: Date/time to format.
    :type arrow_date: :py:class:`arrow.arrow.Arrow`

    :return: Date formatted as `yyyymmdd` digits.
    :rtype: str
    """
    return arrow_date.format("YYYYMMDD").lower()