D.C. Mun. Regs. tit. 29, § 161
161.1 In the computation of time within which an action shall be taken or an appeal filed, the calendar day on which the action occurred shall not be included.
161.2 If the last day that an action may or shall be filed is a Saturday, Sunday, or a legal holiday, that day shall be excluded from the computation of time and the time period shall extend until the end of the next day which is not a Saturday, Sunday, or a legal holiday.
SOURCE: Final Rulemaking published at 38 DCR 2034 (April 5, 1991); as amended by 54 DCR 6020 (June 22, 2007).