Cal. Gov. Code § 31695.2

All eligible employees may elect to be included within the safety member provisions of this chapter by written notice filed with the board not later than 60 days from and after the effective date of the approval of the board of supervisors of the provisions of this article, or within 60 days from and after the effective date of a selection of benefits by the board of supervisors under Section 31808.6, whichever is later.