14 CFR §13.45

1. (a)In computing any period of time prescribed or allowed by this subpart, the date of the act, event, default, notice, or order is not to be included in the computation. The last day of the period so computed is to be included unless it is a Saturday, Sunday, or Federal holiday, in which event the period runs until the end of the next day that is not a Saturday, Sunday, or a Federal holiday.
2. (b)Whenever a party must respond within a prescribed period after service by mail, 5 days are added to the prescribed period.
3. (c)The parties may agree to extend the time for filing any document required by this subpart with the consent of—
   1. (1)The Director of the Office of Adjudication prior to the designation of a hearing officer;
   2. (2)The hearing officer prior to the filing of a notice of appeal; or
   3. (3)The Director of the Office of Adjudication after the filing of a notice of appeal.
4. (d)If the parties do not agree, a party may make a written request to extend the time for filing to the appropriate official identified in paragraph (c) of this section. The appropriate official may grant the request for good cause shown.