California Code, Business and Professions Code - BPC § 7140

All licenses issued under the provisions of this chapter shall expire two years from the last day of the month in which the license is issued, or two years from the date on which the renewed license last expired.

To renew a license which has not expired, the licensee shall, before the time at which the license would otherwise expire, apply for renewal on a form prescribed by the registrar and pay the renewal fee prescribed by this chapter.  Renewal of an unexpired license shall continue the license in effect for the two-year period following the expiration date of the license, when it shall expire if it is not again renewed.