From memory I applied in May for the UMAT, they closed the 12th of June (how I remember that I don't know). Anyway it opened waaay before that I just wasn't sure personally if I was going to apply for med because I wasn't sure if I was going to make it... thank god I applied lol.
I think they open sometime in April...but just put the acer website in your book marks and check it regulary
Oh and a heads up
NSW med. form is due by the end of July
Griffith closes early
Adelaide closes end of August
Tasmainia... I also think closes early too
Anyway apply early! always apply early.