45 C.F.R. § 501.7 – Time.

(a) Computation. In computing any period of time prescribed or allowed by the regulations, by order of the Commission, or by any applicable 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 is to be included, unless it is a Saturday, Sunday or legal holiday, in which event the period runs until the end of the next day that is neither a Saturday, Sunday nor a holiday. When the period of time prescribed or allowed is less than 7 days, intermediate Saturdays, Sundays and holidays will be excluded in the computation.
(b) Enlargement. When by the regulations in this chapter, or by a notice given thereunder or by order of the Commission, an act is required or allowed to be done at or within a specific time, the Commission for good cause shown may, at any time in its discretion:
1. (1) With or without motion, notice, or previous order or
2. (2) Upon motion, permit the act to be done after the expiration of the specified period.