The other poster is correct by saying that there are three time zones in Australia.
Just a little more detail about the three zones:
- Australian Eastern Standard Time (AEST)
This zone covers all eastern states of Queensland, New South Wales (except Broken Hill), Victoria, Tasmania and the ACT.
- Australian Central Standard Time (ACST)
This zone covers South Australia, Broken Hill (western NSW) and the Northern Territory.
- Australian Western Standard Time (AWST)