Change rent in advance

Hi, 

I am looking to change a Tenants Rent going forward.  Today is the Rent Payment Day.  If I go into Change Rent tp set a new Rent, the drop down shows the current Rent Day and the last 3 months, BUT not the next on going forward. 

So I have to wait a day before I can update the system.  If I agree to a Rent change 3 months in advance this would also have the same problem.

Or am I missing something.