In computing any period of time prescribed or allowed by these rules or by any applicable statute, the day of the act, event, or default from which the designated period of time begins to run shall not be included.
The last day of the computed period shall be included unless it is a Saturday, Sunday, or legal holiday, in which event the period shall run until the end of the next day which is not a Saturday, Sunday, or legal holiday.
When the period of time prescribed or allowed is less than seven (7) days, intermediate Saturdays, Sundays, and legal holidays shall be excluded from the computation unless an applicable statute expressly provides otherwise.
Subsection 401.3 of this section does not apply to proceedings pursuant to D.C. Code § 1-1001.08(o) (2006 Repl.).
For the purposes of this chapter, "legal holiday" includes the following:
[Reserved]
When an act is required or allowed to be done at or within a specified time, the Board for cause shown may at any time in its discretion, do either of the following:
D.C. Mun. Regs. tit. 3, r. 3-401