For second holiday of two adjacent ones!
    If holiday falls on Saturday, use following Monday instead;
    if holiday falls on Sunday or Monday, use following Tuesday instead
    (because Monday is already taken by adjacent holiday on the day before)

def next_monday_or_tuesday(dt):
    """
    For second holiday of two adjacent ones!
    If holiday falls on Saturday, use following Monday instead;
    if holiday falls on Sunday or Monday, use following Tuesday instead
    (because Monday is already taken by adjacent holiday on the day before)
    """
    dow = dt.weekday()
    if dow == 5 or dow == 6:
        return dt + timedelta(2)
    elif dow == 0:
        return dt + timedelta(1)
    return dt