I recently signed a lease agreement on 4-21-2012 for 12 months and I'm was told that rent would be due on June 1st for one full month of rent. I had the understanding that when I paid rent and deposit at signing. I was paying for the month of may. However my landlord sent in email that there would be an additional amount due for prorated from 4-21 thrg 4-30. My lease ends on 4-21-2013. So will my last months rent be prorated as well. Or should I pay from the 21st to the 21st each month and vacate by the final month of the lease by the 21st. I so confused...

What does the lease say? If the lease says's rent is due on the 1st, then its due on the first. If the lease doesn't specify what period is covered then you need to clarify this with the landlord. Ask him for an addendum to the lease that you both initial specifying the rental period and that if you move out prior to the end of the rental period (providing sufficient notice is given) that your final rental also be prorated.