Q: I have a renewal offer with increase that was not received within 90 days.

A: I am not sure I follow but it sounds as if you are on a fixed term lease which expires 11/30/20 and now have gotten a renewal offer with a rent raise while only being provided 87 days notice. And you reference the landlord changing the effective date to 12/07/20. It is unclear how the landlord "changed" the effective date and whether that is a lawful change (presumably they could issue an "Amended Notice" with adequate time frames provided. If the above is accurate, the landlord presumably could raise the rent (as long as the raise is otherwise legally compliant) at other than the start of the lease (12/1/20), such as on December 7, 2020 so long as the new lease reflects the two different rental amounts, effective dates, etc. You would owe the original rent amount on a daily pro-rated basis until the new rent kicked in and then owe it going forward (with the balance of December presumably being prorated at the new rent rate). I do note that normally the critical date is when the landlord served it to the tenant, not necessarily when the tenant received it. If served by mail, the landlord must add an additional 4 days (including the day of mailing) to the compliance or effective date (i.e. a 90 day notice becomes a 94 day notice) in order for the notice to be valid. Questions? Problems? Review everything with a local landlord-tenant attorney if you want to know your exact rights in this specific situation. Good luck.