If you check this link,
<a href="http://www.adea.org/AADSAS/calendar.htm" target="_blank">http://www.adea.org/AADSAS/calendar.htm</a>
it is the AADSAS claendar for 2002 cycle it states that the App is avaliable in March. It should be about the same each year. I started filling out my online app then. It allows you to save it and make changes. You can submit it anytime after you get it all filled out. ALSO! You can send it in without DAT scores or you can send updated scores.
Big point here: Be as early as possiable! If your packet is about average, or even upper average, the best ways for you to stand out is to #1 have an early package, #2 have a good, HONEST, letter that reassures them that you can do it and that you will not quit and #3 there is no number 3.
I hope that helps, humor and all, keep asking questions, I feel that the only way I learned how to apply is by asking questions and poking around untill I found a good answer.
Good luck!