When, by notice given under this chapter, or by order or decision of an Examiner, an act is required or allowed to be done at or within a specified time, the Examiner for cause shown may, at any time in his or her discretion, do either of the following:
In computing any period of time prescribed or allowed by this chapter, by notice, order, rule, or regulation of the Department, or by statute, the day of the act, event, or default after which the designated period of time begins to run is not to be included.
The last day of the period so computed shall be included unless it is a Saturday, Sunday, or legal holiday, in which event the period runs until the end of the next day which is not a Saturday, Sunday, or legal holiday.
Whenever a party has the right or is required to take action within the period prescribed by this chapter, by a notice given thereunder, or by an order or regulation, the examiner may, before the expiration of the prescribed period, with or without notice, extend the period; or, upon motion, permit the act to be done after the expiration of the specified period, where the failure to act is clearly shown to have been the result of excusable neglect.
D.C. Mun. Regs. tit. 18, r. 18-1001