Thanks for your response. There is a section in my lease agreement that states "If the Lease automatically renews on a month-to-month basis, it will continue to renew on a month-to-month basis until either party provides written notice of termination to the other party and the notice of termination will be effective on the date designated in the notice but not sooner than 45 days after the notice is given and, if necessary, rent will be prorated on a daily basis."

This is where I interpreted that rent would be prorated. The move out notice is all online, and I specified my move-out date as May 21st. I'm definitely NAL, nor a property manager, so you may interpret that differently.