Not sure exactly when or how they release them, I never study them so far out. I will be looking myself this time though as we have 20 days of DDP to sort for our August trip. Maybe someone else knows.
For August 2009 it wasnt the beginning of February that they came out as it was causing some people issues. I cant remember the exact date but it might have been about a week later?
I tend to go by the previous years opening hours as they seem to be roughly the same to make my draft plans and then make concrete plans when they come out.
like JTlover we use last years as a guide but we do kepp checking for the proper hours (which can change even after being puclished). For August it should be 01/02 (we are there in Auhust so will be checking )