D.C. Mun. Regs. tit. 6, r. 6-B1134
Night differential shall not be paid unless specifically authorized by this section.
An employee who performs regularly scheduled night work between the hours of 6:00 p.m. and 6:00 a.m. shall be entitled to premium pay as provided in § 1134.3.
An employee who performs regularly scheduled nonovertime night work shall be entitled to pay at a rate equal to ten percent (10%) of his or her rate of basic pay for that work, payable on an hour-for-hour basis, in increments of one-quarter (1/4) of an hour for each fifteen (15) minutes and portion thereof in excess of fifteen (15) minutes.
An employee shall be entitled to a night differential for night work performed when he or she is assigned temporarily, except on an overtime basis, to a tour of duty other than his or her own.
Night differential shall not be considered basic pay for any purpose except for computing overtime under the Fair Labor Standards Act.
D.C. Mun. Regs. tit. 6, r. 6-B1134