Cal. Civ. Proc. Code § 321

In every action for the recovery of real property, or the possession thereof, the person establishing a legal title to the property is presumed to have been possessed thereof within the time required by law, and the occupation of the property by any other person is deemed to have been under and in subordination to the legal title, unless it appear that the property has been held and possessed adversely to such legal title, for five years before the commencement of the action.