California Code, Government Code - GOV § 7522.48

(a) Final compensation of a member for the purpose of determining any pension or benefit resulting from service as an elective or appointed officer on a city council or a county board of supervisors accrued while in membership of a public retirement system shall be based on the highest average annual pensionable compensation earned by the member during the period of service in each elective or appointed office. Where that elective or appointed service is a consideration in the computation of any pension or benefit, the member may have more than one final compensation.

(b) Any final compensation calculation shall otherwise be subject to this article except that if any individual period of elective service is less than 36 months or three years, then the entire period of that individual's elected service shall be used to determine the final compensation for that period of service.

(c) This section shall apply to a member first elected or appointed to a city council or a county board of supervisors on or after January 1, 2013.