In general earlier is better but if you have terrible scores and apply early it won't do much either. That being said, I know of two people who took their DATs in late August last year (After the 20th) and both were accepted to their respective state schools in the first wave.
I was admitted with a Mid November App, (Nov. 17). My interviews were all in January and February, and one last minute one in March. I think one of the only things that got my foot in the door was my really high DAT's, and I would NOT suggest that anyone follow what I did! An August app is still fine, but it's less likely that you'll get a Dec 1st admissions - but remember that at least half of the seats are still avalable after that.