Cal. Welf. & Inst. Code § 252

At any time prior to the expiration of 10 days after service of a written copy of the order and findings of a referee, a minor or his or her parent or guardian or, in cases brought pursuant to Section 300, the county welfare department may apply to the juvenile court for a rehearing. That application may be directed to all or to any specified part of the order or findings, and shall contain a statement of the reasons the rehearing is requested. If all of the proceedings before the referee have been taken down by an official reporter, the judge of the juvenile court may, after reading the transcript of those proceedings, grant or deny the application. If proceedings before the referee have not been taken down by an official reporter, the application shall be granted as of right. If an application for rehearing is not granted, denied, or extended within 20 days following the date of its receipt, it shall be deemed granted. However, the court, for good cause, may extend the period beyond 20 days, but not in any event beyond 45 days, following the date of receipt of the application, at which time the application for rehearing shall be deemed granted unless it is denied within that period. All decisions to grant or deny the application, or to extend the period, shall be expressly made in a written minute order with copies provided to the minor or his or her parent or guardian, and to the attorneys of record.