Legal Question in Real Estate Law in California

I am not sure that I really understand what you want. If the premises are not available when specified, the lessee can declare the contract breached by the owner or work out new terms with the owner. The new agreement may very well look exactly like the old except as to dilferent dates.

The landlord is the owner of the premises. He certainly can enter into a contract as to a future event, such as a lease when he gains possession of the property, but it is a gamble for the tenant in a commerical lease.

An example of the answers to your questions is that a tenant gives a 30 day notice to the landlord that they are moving out, the landlord finds a new tenant within that time and agrees to rent it to the new person starting on the 31th day after the notice.