(a) In computing time periods, the term “day” shall mean calendar day.

(b) Except as otherwise provided by law, in computing any period of time prescribed or allowed by this part, or by any notice, order, rule, presiding officer ruling, or regulation of the Commission or a presiding officer, the day of the act, event, or default after which a designated period of time begins to run is not to be included.

(c) The last day of the period so computed is to be included unless it is a Saturday, Sunday, Federal holiday, or a day on which the Commission is not continuously open from 8 a.m. to 4:30 p.m. or on which the Commission's docketing system is not accessible continuously during that time. In any such case, the applicable time period shall run until the end of the next full business day that the Commission is open and its docketing system is accessible.

(d) Except in proceedings to consider changes in the nature of postal services conducted under part 3020 of this chapter, in computing a period of time which is five days or less, all Saturdays, Sundays, Federal holidays, or days on which the Commission is not continuously open from 8 a.m. to 4:30 p.m. or on which the Commission's docketing system is not accessible continuously during that time are to be excluded.