D.C. Mun. Regs. tit. 14, r. 14-3912
Where this chapter or any order of the Rent Administrator specifies a time period, any reference to "days" shall mean all calendar days, unless specifically designated as "business days."
"Business days," where expressly used in this chapter or by order of the Rent Administrator, shall be all days other than Saturdays, Sundays, legal holidays codified at D.C. Official Code § 1-612.02, furlough days, and other closed days as designated by the District of Columbia Government.
In calculating any period of time prescribed or allowed by this chapter or by order of the Rent Administrator, the day of the act, event, or default from which the time period begins to run shall not be included.
In calculating any time period specified by this chapter or by order of the Rent Administrator, the last day of the period shall be included, unless it is not a business day, in which case the period shall end on the next business day.
In accordance with § 3911.5, a party's obligation to serve any petition or other document on another person, if done by U.S. mail, shall be deemed complete on the date of mailing.
If a party is permitted or required to act within a specified time period after an event, such as the issuance of any order or the service of a motion by another party, if the party has been served with the petition or other document by U.S. mail, five (5) days shall be added to the time period for the party to act.
In accordance with § 3901.8, a party's obligation to file any petition or other document with the Rent Administrator shall be deemed complete only upon actual receipt by the Rental Accommodations Division during its business hours, as provided by § 3900.7, regardless of how the filing is made.
The Rent Administrator may enlarge any time period specified in the course of a proceeding, either on motion by a party or on its own initiative in accordance with § 3925.
D.C. Mun. Regs. tit. 14, r. 14-3912