Local law governs in this case.

You lease has expired and the default local law applies. Say in New York, if you don't have a lease or the lease expires, it is deemed to be a month-to-month lease, meaning that the both landlord and tenant have to give 30-day notice to terminate the leasehold. If the same law holds true in your state, your will still have to pay your rent up until the end of April because the 30-day clock starts ticking from the start of the next period, which is April 1st. What you think is not important. Rather what law says is what you will have to find out.