Tex. Gov't Code § 813.402
(a) A member may establish service credit in the elected class for any calendar year during any part of which:
Acts 1981, 67th Leg., p. 1876, ch. 453, Sec. 1, eff. Sept. 1, 1981.
Amended by Acts 1983, 68th Leg., p. 1110, ch. 252, Sec. 3, eff. Aug. 29, 1983. Renumbered from Vernon's Ann.Civ.St. Title 110B, Sec. 23.402 and amended by Acts 1989, 71st Leg., ch. 179, Sec. 1, eff. Sept. 1, 1989.
Amended by Acts 1997, 75th Leg., ch. 1048, Sec. 7, eff. Sept. 1, 1997;
Acts 1999, 76th Leg., ch. 1541, Sec. 10, eff. Sept. 1, 1999.