5 U.S.C. § 8338

(a) An employee who is separated from the service or transferred to a position in which he does not continue subject to this subchapter after completing 5 years of civilian service is entitled to an annuity beginning at the age of 62 years. (b) A Member who, after December 31, 1955 , is separated from the service as a Member after completing 5 years of civilian service is entitled to an annuity beginning at the age of 62 years. A Member who is separated from the service after completing 10 or more years of Member service is entitled to an annuity beginning at the age of 60 years. A Member who is separated from the service after completing 20 or more years of service, including 10 or more years of Member service, is entitled to a reduced annuity beginning at the age of 50 years. (c) A judge of the United States Court of Appeals for the Armed Forces who is separated from the service after completing 5 years of civilian service is entitled to an annuity beginning at the age of 62 years. A judge of such court who is separated from the service after completing the term of service for which he was appointed is entitled to an annuity. If an annuity is elected before the judge becomes 60 years of age, it shall be a reduced annuity. (d) An annuity or reduced annuity authorized by this section is computed under section 8339 of this title .