California Code, Public Resources Code - PRC § 8815.2

The epoch for a survey using CCS83 coordinates shall be the published NGS or CSRC datum realization and epoch date of a published coordinate for a controlling station used for that survey.  These surveys performed after December 31, 1999, shall be based on the “NAD83 (1992) epoch 1991.35” datum realization and epoch or a subsequent published NGS or CSRC datum realization and epoch.