D.C. Mun. Regs. tit. 17, § 4124
4124.1 In computing any period of time specified in this chapter, the day of the act, event, or default shall not be counted, and the last day of the period shall be counted unless it is a Saturday, Sunday, legal holiday, or day on which the Department is officially closed, in which event the time period shall continue until the next day that is not a Saturday, Sunday, legal holiday, or day on which the Department is officially closed.
SOURCE: Final Rulemaking published at 34 DCR 5872 (September 11, 1987).