Notice and acknowledgment of receipt (CCP 415.30): 20 days after mailing for recipient to sign and return; then sender may serve another way and recover expenses

(d) If the person to whom a copy of the summons and of the complaint are mailed pursuant to this section fails to complete and return the acknowledgement form set forth in subdivision (b) within 20 days from the date of such mailing, the party to whom the summons was mailed shall be liable for reasonable expenses thereafter incurred in serving or attempting to serve the party by another method permitted by this chapter, and, except for good cause shown, the court in which the action is pending, upon motion, with or without notice, shall award the party such expenses whether or not he is otherwise entitled to recover his costs in the action.

CCP 12: "The time in which any act provided by law is to be done is computed by excluding the first day, and including the last, unless the last day is a holiday, and then it is also excluded." CCP 12a(a): "If the last day for the performance of any act provided or required by law to be performed within a specified period of time is a holiday, then that period is hereby extended to and including the next day that is not a holiday. For purposes of this section, “holiday” means all day on Saturdays, all holidays specified in Section 135 and, to the extent provided in Section 12b, all days that by terms of Section 12b are required to be considered as holidays." CCP 12b: "If any city, county, state, or public office, other than a branch office, is closed for the whole of any day, insofar as the business of that office is concerned, that day shall be considered as a holiday for the purposes of computing time under Sections 12 and 12a." CCP 10: "Holidays within the meaning of this code are every Sunday and any other days that are specified or provided for as judicial holidays in Section 135."