Cal. Bus. & Prof. Code § 6795

Certificates of registration as a professional engineer, and certificates of authority, shall be valid for a period of two years from the assigned date of renewal. Biennial renewals shall be staggered on a quarterly basis. To renew an unexpired certificate, the certificate holder shall, on or before the date of expiration indicated on the renewal receipt, apply for renewal on a form prescribed by the board, and pay the renewal fee prescribed by this chapter.