(a) In general. In computing any period of time prescribed by the rules in this part or allowed by the Commission, the Director of the Office of Proceedings, an Administrative Judge, or an Administrative Law Judge, the day of the act, event, or default from 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, a Sunday, or a legal holiday, in which event the period runs until the end of the next day which is not a Saturday, a Sunday, or a legal holiday. Intermediate Saturdays, Sundays, and legal holidays shall be excluded from the computation only when the period of time prescribed or allowed is less than seven (7) days.

(b) Date of service of orders. In computing any period of time involving the date of service of an order, the date of service shall be the date the order is served by the Proceedings Clerk, which, unless otherwise indicated, shall be the date stamped on the order by the Proceedings Clerk.