Australia has three time zones:
Central Standard Time (CST) in the middle of Australia, covering the Northern Territory and South Australia;
Western Standard Time, covering Western Australia;
Eastern Standard Time, covering Queensland, New South Wales, the Australian Capital Territory, Victoria and Tasmania.

Eastern Standard Time is 30 minutes in front of Central Standard Time; and Western Standard Time is 90 minutes behind. For example, if it is midday in the Northern Territory, it will be 12.30 pm in the Eastern states and 10.30 am in Western Australia.

However, this formula is somewhat complicated in the summer months by the introduction of daylight saving in some states.

New South Wales and the Australian Capital Territory have daylight saving from November to February,

South Australia and Victoria from November to March

Tasmania from October to March.

This takes the clock back one hour. For example, if it is midday in the Northern Territory, it will be 1 pm in South Australia and 1.30 pm in New South Wales.

The Northern Territory, Western Australia and Queensland ignore it completely.