California Code, Family Code - FAM § 8601.5

(a) A court may issue an order of adoption and declare that it shall be entered nunc pro tunc when it will serve public policy and the best interests of the child, such as cases where adoption finalization has been delayed beyond the child's 18th birthday due to factors beyond the control of the prospective adoptive family and the proposed adoptee.

(b) The request for nunc pro tunc entry of the order shall be stated in the adoption request or an amendment thereto, and shall set forth specific facts in support thereof.

(c) To the extent that a child's eligibility for any publicly funded benefit program is or could be altered by the entry of an order of adoption, the change in eligibility shall not be determined as of the nunc pro tunc date, but shall be determined as of the date of the adoption finalization hearing.

(d) The nunc pro tunc date shall not precede the date upon which the parental rights of the birth parent or parents were initially terminated, whether voluntarily or involuntarily.