5 U.S.C. § 3305: Competitive service; examinations; when held

(a) The Office of Personnel Management shall hold examinations for the competitive service at least twice a year in each State and territory or possession of the United States where there are individuals to be examined. (b) The Office shall hold an examination for a position to which an appointment has been made within the preceding 3 years, on the application of an individual who qualifies as a preference eligible under section 2108(3)(C)–(G) of this title. The examination shall be held during the quarter following the application.