California Code, Probate Code - PROB § 19023

At least 30 days before the time set for the hearing on the petition, the petitioner shall cause notice of the time and place of the hearing and a copy of the petition to be served on each of the creditors whose interests in the estate may be affected by the petition in the manner provided in Chapter 4 (commencing with Section 413.10) of Title 5 of Part 2 of the Code of Civil Procedure.