California Code, Government Code - GOV § 31462.2

(a) “Final compensation” for members whose service is on a tenure that is temporary, seasonal, intermittent, or for part time only means one-third of the total compensation earnable earned for that period of time during which the member rendered the equivalent of three years of full-time service.

(b) The member may elect at or before the time the member files an application for retirement the period of time during which the member has earned three full years of credit upon which final compensation shall be calculated. If the member does not so elect, that period of time immediately preceding their retirement shall be used.

(c) This section also applies to a member meeting the conditions specified in subdivision (a), whose service is described in subdivision (a), and who is subject to the California Public Employees' Pension Reform Act of 2013 (Article 4 (commencing with Section 7522) of Chapter 21 of Division 7 of Title 1).