Section 13.27 - Computation of time(a) In computing any period of time under this part or in an order issued thereunder, the time begins with the day following the act, event, or default, and includes the last day of the period, unless it is a Saturday or Sunday, a Federal legal holiday at the place where the action or event is to occur, or a day on which, because of emergency closure of the federal government in Washington, DC, NRC Headquarters does not open for business, in which event it includes the next day that is not a Saturday, Sunday, holiday or emergency closure.(b) When the period of time allowed is less than seven (7) days, intermediate Saturdays, Sundays, Federal legal holidays, and emergency closures shall be excluded from the computation.(c) Whenever an action is required within a prescribed period by a document served pursuant to § 13.26 , no additional time is added to the prescribed period except in the following circumstances:(1) If a notice or document is served upon a participant, by first-class mail only, three (3) calendar days will be added to the prescribed period for all the participants in the proceeding.(2) If a notice or document is served upon a participant, by express mail or other expedited service only, two (2) calendar days will be added to the prescribed period for all the participants in the proceeding.(3) If a document is to be served by multiple service methods, such as partially electronic and entirely on an OSM, the additional number of days is computed according to the service method used to deliver the entire document, excluding courtesy copies, to all of the other participants in the proceeding. The presiding officer may determine the calculation of additional days when a participant is not entitled to receive an entire filing served by multiple methods.(4) In mixed service proceedings where all participants are not using the same filing and service method, the number of days for service will be determined by the presiding officer based on considerations of fairness and efficiency. The same number of additional days will be added to the prescribed period for all the participants in the proceeding with the number of days being determined by the slowest method of service being used in the proceeding.(d) To be considered timely, a document must be served:(1) By 5 p.m. Eastern Time for a document served in person or by expedited service; and(2) By 11:59 p.m. Eastern Time for a document served by the E-Filing system. 72 FR 49153 , Aug. 28, 2007