As used in § 5-521.01, the word “holiday” means the following: The 1st day of January, the 3rd Monday in February, the 4th day of July, the last Monday in May, the 1st Monday in September, the 2nd Monday in October, the 4th Monday in October, Thanksgiving Day, the 25th day of December, and, with respect to officers and members of the Metropolitan Police force and the Fire Department of the District of Columbia, such other holidays as may be designated by the Council of the District of Columbia, and with respect to officers and members of the United States Park Police force, such other holidays as may be designated by executive order.