Why the source clause matters
In Plaza Freeway Ltd. Partnership v. First Mountain Bank, a commercial lease gave the tenant a renewal option exercisable with advance notice. The parties had never documented the actual commencement date, the tenant had certified a termination date in an estoppel certificate, and the court held the tenant to that certified date, which made its renewal notice untimely. The case is specific to its facts and California law, but it shows how a date that was never pinned to a clear source can decide whether a right survives.