Daylight saving time in Australia

Daylight saving time (DST) is currently observed in the Australian states of New South Wales, South Australia, Tasmania, and Victoria, as well as the Australian Capital Territory, Jervis Bay Territory and Norfolk Island. Other Australian jurisdictions – the states of Queensland and Western Australia, the Northern Territory and Australia's other external territories – do not observe daylight saving time.

Each state and territory determines whether or not to use daylight saving time. During World War I and World War II all states and territories had daylight saving by federal law,^[1] under the defence power in section 51 of the constitution. In 1968, Tasmania was the first state since the war to adopt daylight saving. In 1971, New South Wales, Queensland, South Australia, Victoria, and the Australian Capital Territory also adopted daylight saving, while Western Australia and the Northern Territory did not. Queensland abandoned daylight saving in 1972. Queensland and Western Australia have subsequently observed daylight saving on a trial basis on several occasions.

As a result of the inconsistent adoption of daylight saving, during the Australian summer the mainland's three standard time zones increase to five time zones. South Australia time diverges from Northern Territory time to become UTC+10:30, known as Central Daylight Time (CDT) or Australia Central Daylight Time (ACDT), while the time in the southeastern states diverges from Queensland time to become UTC+11:00, known as Eastern Daylight Time (EDT) or Australia Eastern Daylight Time (AEDT).

Officially, the change to and from DST takes place at 02:00 local standard time (which is 03:00 DST) on the appropriate Sunday. Of the states that observe DST, most began on the last Sunday in October, and ended on the last Sunday in March, until 2007. Tasmania, owing to its further southern latitude began DST earlier, on the first Sunday in October, and ended on the last Sunday in March. In the 2007–08 season, Tasmania started on the first Sunday in October whilst the ACT, NSW, Vic and SA started in the last Sunday in October. As part of the transition to earlier daylight saving, those states and Tasmania all finished on the first Sunday in April. For subsequent years, DST in the south-eastern states and SA now starts on the first Sunday in October, finishing on the first Sunday in April the next year. Western Australia was not affected by these changes to DST, being the only state in 2007–08 to observe daylight saving from the last Sunday in October to the last Sunday in March. However, since 2009, it is on Standard time all year round.^[2]