D.C. Mun. Regs. tit. 17, § 3337
3337.1 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 not a business day, in which event the time period shall continue until the next business day.
SOURCE: Final Rulemaking published at 35 DCR 3488, 3516 (May 13, 1988).