Section 7(o) provides as follows:
In the case of employees described in clause (A)(ii) hired prior to April 15, 1986, the regular practice in effect on April 15, 1986, with respect to compensatory time off for such employees in lieu of the receipt of overtime compensation, shall constitute an agreement or understanding under such clause (A)(ii). Except as provided in the previous sentence, the provision of compensatory time off to such employees for hours worked after April 14, 1986, shall be in accordance with this subsection.
29 C.F.R. §553.21