Cal. Gov. Code § 9359
Upon his or her written application to the Board of Administration, (a) a member of this system who was a member on the effective date of this amendment who has attained 60 years of age, (b) a member who hereafter becomes a member of this system who has attained 60 years of age and who is credited with 4 or more years of service, or (c) a member, regardless of age, who is credited with 20 or more years of service, shall be retired, and thereafter shall receive for life the retirement allowance provided in this chapter.
A written application for retirement may be filed at any time during the term of office of the member, or within 30 days after the expiration of his or her term of office. An application that does not specify a different date as the effective date of retirement applied for shall be deemed to be an application for retirement as of the day following the expiration of the term of office of the member.
Ca. Gov. Code § 9359