D.C. Code § 1-1021.01: Timeliness of action.

For purposes of this or any other act administered by the Board of Elections and Ethics, if the final date for any action falls on a Saturday, Sunday, or legal holiday, such action shall be considered timely if taken on the next regular business day immediately thereafter; provided, that if the action is required for compliance with the Uniformed and Overseas Citizens Absentee Voter Act, approved August 28, 1986 (100 Stat. 924; 42 U.S.C. § 1973ff et seq.), and the final date for completing the action falls on a Saturday, Sunday, or legal holiday, it shall be considered timely if taken on the immediately preceding regular business day.