def wkday_to_mon0(day):
    """Converts an integer weekday number to a representation where Monday is 0
    and Sunday is 6 (the datetime default), from a representation where Sunday
    is 0, Monday is 1 and Saturday is 6 (the strftime behavior).

    :param day: The weekday number [0(Sunday)..6]
    :type day: integer

    :returns: The weekday number [0(Monday)..6]
    :rtype: integer

    """
    if day == 0:
        return 6
    else:
        return day - 1
