Landlord Question and Answer Forum

I'm in California. Our current tenant gave their 60 day notice to vacate on 8/22 (so essentially until 10/22). They closed Escrow on their new home on 9/10 and were planning on moving out around that time no matter what. I was able to find a new tenant who signed a lease on 9/16 to take over on 9/20... information of which I communicated to my current tenant. 3 days after signing the new tenant called to ask if they can change the start date to 10/1 because they are having issues with their escrow. I'd like to help them out, but can I now go back to my current tenant to say the lease was changed to start on 10/1 and hold them responsible for those 10 days of rent since it falls within the 60-day period? Or am I stuck either taking a loss personally or holding the new tenant to the initial start date?