Under California law, you must give notice of termination of your month-to-month lease a full 30 days before the beginning of the next month's rental period. If you occupy the apartment during any part of a month, you are assumed to have renewed your rental agreement for the entire month. Since you will have occupied the unit for some portion of March, you renewed your month-to-month lease for the full month. Your notice of termination therefore applies to the upcoming month's lease and your tenancy will terminate at the end of March. If you move out early and your landlord re-rents the until prior to the end of March you are owed a partial refund of the month's rent. California Civil Code Section 1946.