Fam. Code, § 4

(a) As used in this section:

(1) “New law” means either of the following, as the case may be:

(A) The act that enacted this code.

(B) The act that makes a change in this code, whether effectuated by amendment, addition, or repeal of a provision of this code.

(2) “Old law” means the applicable law in effect before the operative date of the new law.

(3) “Operative date” means the operative date of the new law.

(b) This section governs the application of the new law except to the extent otherwise expressly provided in the new law.

(c) Subject to the limitations provided in this section, the new law applies on the operative date to all matters governed by the new law, regardless of whether an event occurred or circumstance existed before, on, or after the operative date, including, but not limited to, commencement of a proceeding, making of an order, or taking of an action.

(d) If a document or paper is filed before the operative date, the contents, execution, and notice thereof are governed by the old law and not by the new law; but subsequent proceedings taken after the operative date concerning the document or paper, including an objection or response, a hearing, an order, or other matter relating thereto is governed by the new law and not by the old law.

(e) If an order is made before the operative date, or an action on an order is taken before the operative date, the validity of the order or action is governed by the old law and not by the new law. Nothing in this subdivision precludes proceedings after the operative date to modify an order made, or alter a course of action commenced, before the operative date to the extent proceedings for modification of an order or alteration of a course of action of that type are otherwise provided in the new law.

(f) No person is liable for an action taken before the operative date that was proper at the time the action was taken, even though the action would be improper if taken on or after the operative date, and the person has no duty, as a result of the enactment of the new law, to take any step to alter the course of action or its consequences.

(g) If the new law does not apply to a matter that occurred before the operative date, the old law continues to govern the matter notwithstanding its repeal or amendment by the new law.

(h) If a party shows, and the court determines, that application of a particular provision of the new law or of the old law in the manner required by this section or by the new law would substantially interfere with the effective conduct of the proceedings or the rights of the parties or other interested persons in connection with an event that occurred or circumstance that existed before the operative date, the court may, notwithstanding this section or the new law, apply either the new law or the old law to the extent reasonably necessary to mitigate the substantial interference.