A prior section 251 of Pub. L. 88–643, title II, Oct. 13, 1964, 78 Stat. 1050; Pub. L. 94–522, title II, § 210, Oct. 17, 1976, 90 Stat. 2471; Pub. L. 99–169, title VII, § 702, Dec. 4, 1985, 99 Stat. 1008; Pub. L. 99–335, title V, § 501(2), June 6, 1986, 100 Stat. 622, related to computation of length of service and was set out as a note under section 403 of this title prior to the general amendment of Pub. L. 88–643 by section 802 of Pub. L. 102–496.

Section effective on first day of fourth month beginning after Oct. 24, 1992, see section 805 of Pub. L. 102–496, set out as a note under section 2001 of this title.