California Code, Government Code - GOV § 21006

(a) “Leave of absence” also means any time during which a state member was excused from performance of his or her duties on approved leave for the purpose of further education.  Any member electing to receive service credit for that leave of absence shall make the contributions as specified in Sections 21050 and 21052.  However, any eligible member who applies to make that election between January 1, 2001, and December 31, 2003, may, instead of making those contributions, make the payment calculated under this article as it read on December 31, 2000, which payment shall be made in the manner described in Section 21050.

(b) Credit granted under this section may not exceed two years.

(c) This section shall be applicable to persons who are members or became members of this system on and after January 1, 1975.