The actual release is gonna be staggered to the release of the game in the USA whatever time zone gearbox uses. I assume Central do to the fact they are stationed in Texas and have the central time. So with that said people in Australia will actually have to wait till the fourth so the world will start all together.
Well Gearbox has a reason they are a US company as well as most companies know that the US is the largest base of gamers thus they target us and make us their target. This is why Usually Pacific or Eastern Times are used because they are the usual times and people are used to seeing it.
With that said the beta was pacific time if im not mistaken so i take back what i said about central and will prob pin it to pacific time so use your global time calculators or whatever and find out when it actually releases for you.