Half-hour time zone and having time meridian outside its borders make South Australia an international oddity

South Australia's Australian central standard time zone stands out for oddity of its half-hour time difference.

South Australia’s time zone is an international oddity. By having a half-hour interval from adjacent Australian states' time zones and by having its time meridian outside its boundaries, South Australia departs from the international norms.

The standardising of Australian time zones started in 1892 when surveyors from the six dominions met in Melbourne and accepted Greenwich Mean Time (GMT) as the basis for three zones: western, central and eastern.

From 1895, Western Australia would set its clocks eight hours ahead of GMT, South Australia (and the Northern Territory which South Australia then governed) by eight hours, and Queensland, New South Wales, Victoria and Tasmania by 10 hours.

But, in 1899, as a compromise especially to rural interests, South Australia advanced central standard time by 30 minutes. Attempts to correct this half-hour oddity have been raised in 1986, 1994 and 2015. Broken Hill is far west New South Wales also adopted central standard time, since it had a rail link to Adelaide, but not Sydney, at the time.

Another small anomaly is the unofficial central western standard time (CWST), used in an area of the south eastern Western Australia and one South Australian roadhouse. Towns east of Caiguna on the Eyre Highway and Border Village, just over the border into South Australia, follow central western standard time.

In 1971, South Australia followed Tasmania and joined New South Wales, Victoria, Queensland (since reverted) and Australian Capital Territory in adopting daylight saving time. South Australian daylight saving begins on the first Sunday in October and ends on the first Sunday in April.