CA Civ Proc Code Section 583.230

The parties may extend the time within which service must be made pursuant to this article by the following means:

(a)

By written stipulation. The stipulation need not be filed but, if it is not filed, the stipulation shall be brought to the attention of the court if relevant to a motion for dismissal.

(b)

By oral agreement made in open court, if entered in the minutes of the court or a transcript is made.