(a)Computation. In computing any period of time prescribed or allowed by these rules, except as otherwise provided, the day of the act, event, or default from which the designated period of time begins to run shall not be included. Saturdays, Sundays, and legal holidays shall be included in computing the time allowed for the filing of any document or paper, except that when such time expires on a Saturday, Sunday, or legal holiday, such period shall be extended to include the next following business day.(b)Enlargement. When by these rules or by order of the Administrative Law Judge, the Presiding Officer, or the Environmental Appeals Board, an act is required or allowed to be done at or within a specified time, the Administrative Law Judge (before his initial decision is filed), or the Presiding Officer (before his recommended decision is filed), or the Environmental Appeals Board (after the Administrative Law Judge's initial decision or the presiding officer's recommended decision is filed), for cause shown may at any time in their discretion: with or without motion or notice, order the period enlarged if request therefor, which may be made ex parte, is made before the expiration of the period originally prescribed or as extended by a previous order; or on motion made after the expiration of the specified period, permit the act to be done where the failure to act was the result of excusable neglect. In this connection, consideration shall be given to the fact that, under the provisions of the act, the Administrator must issue his order not later than 90 days after the completion of the hearing, unless all parties agree by stipulation to extend this period of time pursuant to § 164.103 .(c)Additional time after service by mail. A prescribed period of time within which a party is required or permitted to do an act shall be computed from the time of service, except that when the service is made by mail, 3 days shall be added to the prescribed period. Such addition for service by mail shall not apply in the case of filing initial requests for hearings or responding to a notice of intent to hold a hearing, in which cases statutory filing times will run from the date of the return receipt pursuant to § 164.8 .38 FR 19371, July 20, 1973, as amended at 57 FR 5342, Feb. 13, 1992