Cal. Civ. Proc. Code § 1240.210

For the purposes of this article, the “date of use” of property taken for public use is the date when the property is devoted to that use or when construction is started on the project for which the property is taken with the intent to complete the project within a reasonable time. In determining the “date of use,” periods of delay caused by extraordinary litigation or by failure to obtain from any public entity any agreement or permit necessary for construction shall not be included.