5 C.F.R. § 841.109 Computation of time.
Title 5 - Administrative Personnel
In computing a period of time for filing documents, the day of the action or event after which the designated period of time begins to run is not included. The last day of the period is included unless it is a Saturday, a Sunday, or a legal holiday; in this event, the period runs until the end of the next day which is not a Saturday, a Sunday, or a legal holiday.
Title 5: Administrative Personnel
PART 841—FEDERAL EMPLOYEES RETIREMENT SYSTEM—GENERAL ADMINISTRATION
Subpart A—General Provisions
§ 841.109 Computation of time.

