California Code, Government Code - GOV § 21013

“Leave of absence” also means any time, up to one year, during which a member is granted an approved maternity or paternity leave and returns to active state service at the end of the approved leave for a period of time at least equal to that leave. Any member may elect to receive service credit for that leave of absence at any time prior to retirement by making the contributions as specified in Sections 21050 and 21052. This section applies to both past and future maternity or paternity leaves of absences by members of the system.