Per-day still has errors when leap-seconds and daylight savings get involved. It's just a smaller error. And unless you can convince landlords nationwide to cha

Per-day still has errors when leap-seconds and daylight savings get involved. It's just a smaller error. And unless you can convince landlords nationwide to change how billing works, a company creating a monthly billing service is just going to find another developer that makes what they want. edit: Also this may not be typical in every lease, but all of my leases have established the rate as both a yearly and monthly amount. I'm sure my landlord wouldn't complain if I paid all 12 months up front. That's the only truly "fair" way.