Cal. Government Code § 68547

(a) For the purposes of this article, a judge or justice is deemed to serve or sit under assignment on each day during which it is necessary for him or her on account of the assignment to serve in a substantial way on the court to which assigned, to travel to or from such court, or to be absent from his or her residence. If a judge so serves under assignment in one or more courts during all days other than Saturdays, Sundays, and holidays in any period of 30 or more consecutive days (inclusive of Saturdays, Sundays, and holidays), he or she shall be deemed also to have served or sat in such court or courts on all Saturdays, Sundays, and holidays during or immediately preceding that period. If a judge who serves his or her court on a part-time basis has completed the business of the home court for all days affected by any assignment, compensation attributable to the home court shall only be deducted from the amounts to be paid pursuant to Section 68540.7 for the days the judge is serving on assignment to the extent necessary to limit the assigned judge’s total judicial compensation for the month to the amount earned by a regular judge of the court to which the judge is assigned. (b) This section shall become operative on January 1, 2001.