5 CFR § 846.301
General rules
November 4, 2020
(a) An individual who becomes covered by FERS as a result of an election under §846.201 is subject to the provisions of chapter 84 of title 5, United States Code and parts 841 through 845 of this chapter, except as provided in this part.
(b) Civilian service performed before the effective date of the election under §846.201 is not creditable under FERS except as provided in this part.