Time zone · Oceania
ACST
Australian Central Standard Time
Australian Central Standard Time (ACST) covers a UTC+09:30 band stretching across South Australia, the Northern Territory, and a corner of New South Wales. For those coordinating across Adelaide, Darwin, and Broken Hill, it’s a unique half-hour offset that only partially shifts for daylight savings—so scheduling always needs a second check.
Thursday, October 15, 2026
Current offset
UTC+09:30
Standard · ACST
Daylight saving
Not active
Year-round standard time
IANA zones
3
2 observe DST, 1 doesn't
DST offset
UTC+10:30
ACDT · +1h
About ACST
Standard time, with a summer shift.
Australian Central Standard Time (ACST) covers a UTC+09:30 band stretching across South Australia, the Northern Territory, and a corner of New South Wales. For those coordinating across Adelaide, Darwin, and Broken Hill, it’s a unique half-hour offset that only partially shifts for daylight savings—so scheduling always needs a second check.
IANA zones · the technical identifiers
The 3 zones that resolve to ACST.
For software, always store the IANA identifier — never the abbreviation alone. The database keeps these zones distinct because their rules can, and historically did, diverge.
Cities across ACST
Local time, city by city.
1 city
Where ACST is used
One country.
Convert
ACST to the world's clocks.
Frequently asked questions
Common questions about ACST, daylight saving, and how to handle it in software. Can't find what you need? Email [email protected].
- Why does Australia use a half-hour offset like UTC+09:30?
- The half-hour offset reflects the vast east-west span of the continent. ACST aligns clocks more closely with local sunrise and sunset in central Australia rather than forcing the region into a full-hour slot.
- Which parts of ACST observe daylight saving?
- In ACST, Adelaide and Broken Hill move their clocks forward by an hour during southern summer, while Darwin stays on standard time all year. This split means your ACST contacts may suddenly be an hour apart from each other when DST starts.
- How many distinct time zones use ACST?
- Three zones fall under the ACST umbrella: Adelaide, Broken Hill and Darwin. They share the same wall-clock time for much of the year but diverge as soon as daylight saving kicks in.
- What happens in Broken Hill that makes it different?
- Broken Hill sits in western New South Wales but follows South Australia’s ACST schedule, including DST. So while most of NSW uses AEST/AEDT, Broken Hill marches to the Adelaide drum.
- Why doesn’t Darwin observe daylight saving?
- Darwin sits close to the equator, where daylight hours stay fairly constant year-round. The Northern Territory decided the hassle of changing clocks wasn’t worth the minimal benefit, so it stays on standard time permanently.
- Does the entire ACST region change clocks at the same time?
- Adelaide and Broken Hill both spring forward at 2:00 AM local time and fall back at 3:00 AM local time, but Darwin doesn’t change at all. So during DST, you end up with a one-hour split inside the ACST code.
- Is ACST used anywhere besides Australia?
- No. Today UTC+09:30 is used only in Australia: South Australia, the Northern Territory and Broken Hill in New South Wales.
- What should remote teams keep in mind when working with ACST colleagues?
- Always clarify which Australian city—or at least which zone—your contact is in, especially around October and April when Adelaide and Broken Hill flip their clocks. A shared calendar tool like timezone.io saves a lot of “wait, are you in Darwin or Adelaide?” messages.
Source: IANA tzdb2026d · Reviewed
Free · Developer API
This time zone, as JSON.
Its defining offset, DST status and member counts, from one endpoint.
Also in the API: time zones by coordinates, conversions that flag daylight saving gaps, and abbreviations decoded.
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