How much do apartments charge for part of the month?

Our lease is up on May 9th. Our rent is 1,310 and they are charging us almost $900!! I figured that they would charge about $400. I'm going to go down and talk to them about it in the office. They had to have made a mistake because doesn't that sound a little ridiculous for 9 days??? Has anyone had a similar experience with this before? If so please let me know what should be done.

I can't speak for how any other landlords do it but when I have tenants move in during the month, I pro-rate the FIRST months rent. So if you moved in Jan 15 and the rent was $1,000, you would pay $500 for Jan and your lease would be from Jan 15, 2008 to Dec 31, 2008 or 11-1/2 months.

There is enough to keep track of without having leases end on different during the month.

Some places won't let you PAY for a partial month. You pay for the whole month, even if you're only there for a week. I'm moving in March and my last rent payment with be for the entire month, even though I'm moving before the 10th of that month. I'm also paying a month's rent for the place I'm moving to, even though I won't be there until the second WEEK of that month. They don't (or won't) pro-rate.