ACST Time Now

What this page shows

So you want to know what time it is in central Australia right now. Maybe you have a call with Adelaide, something to sort out in the Northern Territory, or a flight routing through that part of the country. That is what the clock at the top of this page is for. It shows the current time in the Australian Central zone and ticks forward every second, so there is nothing for you to work out by hand.

Wherever in the world you are reading this from, the clock tracks Central Australian time and keeps itself right on its own, even across the days when the clocks change. Whether the zone is on ACST or ACDT at the time, the clock shows the correct local time.

The ACST and ACDT thing worth knowing

Here is the part that trips people up, though. You looked for ACST, and this page is labeled ACST, but central Australia does not stay on ACST all year. For the warmer months it runs on daylight saving, under its own name, Australian Central Daylight Time, or ACDT.

And there is a southern hemisphere twist. Australia sits below the equator, so its summer falls at the other end of the year from Europe and North America. Daylight saving there runs through the southern summer, roughly October to April, which is the opposite half of the year from the northern one.

So there are two settings hiding behind the word central:

• ACST, Australian Central Standard Time. Nine and a half hours ahead of UTC, written UTC plus 9:30. The winter setting, used from about April to October.
• ACDT, Australian Central Daylight Time. Ten and a half hours ahead of UTC, written UTC plus 10:30, one hour ahead of ACST. The summer setting, used from about October to April.

What ACST actually is

ACST stands for Australian Central Standard Time, and it sits nine and a half hours ahead of UTC, written as UTC plus 9:30. Like India, it is one of the few zones that runs on a half hour rather than a whole number of hours. It is the middle of Australia's three main zones, half an hour behind the eastern states and an hour and a half ahead of Western Australia.

There is one catch worth flagging. The central zone is shared by two places that treat daylight saving differently. South Australia, with its capital Adelaide, does observe it and moves to ACDT each summer. The Northern Territory, with Darwin, does not, and stays on ACST all year. So the same ACST label covers one area that switches and one that does not. This page follows South Australia, which is the one that changes.

How to tell if it is ACST or ACDT right now

In Australia, daylight saving is decided state by state, and South Australia is one of the states that observes it. The change lands on two Sundays, the same ones the other observing states use:

• Spring forward. On the first Sunday of October, the clocks jump ahead one hour. ACST becomes ACDT, and the zone moves from UTC plus 9:30 to UTC plus 10:30. Daylight saving has begun, in the southern spring.
• Fall back. On the first Sunday of April, the clocks drop back one hour. ACDT becomes ACST again, and the zone returns to UTC plus 9:30.

So the rule is short, just mirrored from the northern one. From the first Sunday of October to the first Sunday of April, South Australia is on ACDT. For the rest of the year, April round to October, it is on ACST. The Northern Territory stays on ACST throughout. Place today between those two Sundays and you have your answer.

Converting ACST to other time zones

The gaps within Australia stay fixed in the parts that do not change clocks, so the table below works from standard ACST at UTC plus 9:30. In the southern summer, when South Australia is on ACDT, add one hour to the Australian side. Here is the quick reference, assuming it is 12 noon ACST.

One thing to keep in mind for Europe and the Americas. Because Australia runs daylight saving in the opposite half of the year, the gap between central Australia and a place like London or New York can swing by up to two hours across the year, as the two sides move on and off their own summer time. For those, the live clock above is the safe bet.

A few quick examples

Let us run a few, so you can see how this works.

Say it is 12 noon in Adelaide in the winter, on ACST. The eastern states are half an hour ahead, so it is 12:30 in the afternoon in Sydney and Brisbane. Perth, over in the west, is an hour and a half behind, at 10:30 in the morning. Japan is half an hour behind, making it 11:30 in the morning in Tokyo.

Now the summer twist. Come the southern summer, Adelaide springs forward to ACDT and is now ten and a half hours ahead of UTC. Brisbane, up in Queensland, does not change, so the gap between Adelaide and Brisbane flips: instead of being half an hour behind the east, Adelaide is now half an hour ahead of Brisbane, though still behind Sydney, which has also sprung forward.

That swapping around inside Australia each summer is exactly why it pays to check the live clock rather than trust a single remembered offset.

Where Central Australian time is used

The central zone covers South Australia, with its capital Adelaide, and the Northern Territory, with Darwin. Both sit at UTC plus 9:30 in winter. The town of Broken Hill, although it is in New South Wales, also keeps central time rather than eastern, a quirk of being out near the South Australian border.

The difference between the two main areas shows up in summer. South Australia moves to ACDT, while the Northern Territory stays on ACST all year. For the zones on either side, eastern Australia sits half an hour ahead and Perth in the west sits an hour and a half behind. You can compare against the eastern states at AEST Time Now and a specific eastern city at Sydney time now.

Questions people ask

What time is it in ACST right now?

The clock near the top of this page is the answer, and it updates every second. Just remember that South Australia observes daylight saving, so that clock shows ACST through the southern winter and ACDT through the southern summer, switching over on its own. Whichever it is, the time shown is the correct local time.

Is it ACST or ACDT at the moment?

Go by the dates. In South Australia, ACDT runs from the first Sunday of October to the first Sunday of April, the southern summer. The rest of the year it is on ACST. The Northern Territory stays on ACST all year. Find where today falls between those two Sundays and you will know.

How many hours ahead of UTC is ACST?

Nine and a half hours ahead, written UTC plus 9:30. When South Australia is on daylight saving as ACDT, it is ten and a half hours ahead, UTC plus 10:30.

Does all of central Australia change its clocks?

No. South Australia and Adelaide observe daylight saving and switch to ACDT each summer. The Northern Territory and Darwin do not, and stay on ACST all year, even though both share the central zone.

Why is Australian daylight saving in the opposite months?

Because Australia is in the southern hemisphere, where summer falls around December to February. Daylight saving runs through the warmer half of the year, so it lands in the southern spring and summer, from October to April, the reverse of Europe and North America.

What is the IANA name for Central Australian time?

It is Australia/Adelaide for the South Australian version that observes daylight saving, in the IANA time zone database your phone and your computer use. Darwin, which does not change, uses Australia/Darwin. Australia/Adelaide is what drives the live clock on this page.

References

1. Internet Assigned Numbers Authority (IANA). Time Zone Database (the tz database), home of the Australia/Adelaide and Australia/Darwin identifiers. https://www.iana.org/time-zones
2. National Measurement Institute (NMI), Department of Industry, Science and Resources, which maintains UTC(AUS), the legal standard for time in Australia under the National Measurement Act 1960. https://www.industry.gov.au/national-measurement-institute/nmi-services/physical-measurement-services/time-and-frequency-services
3. Bureau International des Poids et Mesures (BIPM), Time Department, which maintains Coordinated Universal Time (UTC), the reference Australian time is set against. https://www.bipm.org/en/work-programme/time