5 U.S.C. § 6104

When a regular employee as defined by section 2105 of this title or an individual employed regularly by the government of the District of Columbia, whose pay is fixed at a daily or hourly rate, or on a piece-work basis, is relieved or prevented from working on a day— (1) on which agencies are closed by Executive order, or, for individuals employed by the government of the District of Columbia, by order of the Mayor; (2) by administrative order under regulations issued by the President, or, for individuals employed by the government of the District of Columbia, by the Council of the District of Columbia; or (3) solely because of the occurrence of a legal public holiday under section 6103 of this title , or a day declared a holiday by Federal statute, Executive order, or, for individuals employed by the government of the District of Columbia, by order of the Mayor; he is entitled to the same pay for that day as for a day on which an ordinary day’s work is performed.