Does it account for Daylight Saving Time?

Yes, our converter uses the IANA timezone database, which includes all current DST rules for every timezone in the world.

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. All timezones are defined as offsets from UTC.

Can I compare multiple timezones at once?

Yes, you can add multiple cities or timezones and see the equivalent times side by side.

How many timezones are there in the world?

There are 38 distinct UTC offsets in use, ranging from UTC-12 to UTC+14. This includes half-hour (UTC+5:30 India, UTC+9:30 Australia) and 45-minute offsets (UTC+5:45 Nepal, UTC+8:45 Australia).

What is the International Date Line?

The International Date Line (IDL) runs roughly along the 180° meridian in the Pacific Ocean. When you cross it westward, you gain a day; crossing eastward, you lose a day.

Why do some timezones have 30 or 45 minute offsets?

Countries chose offsets that best matched their solar noon. India uses UTC+5:30 and Nepal uses UTC+5:45 because standard hourly offsets didn't align well with their geography.

Which country has the most timezones?

France has the most (12 timezones) due to overseas territories. Russia spans 11 timezones. The US has 6 (including Hawaii and Alaska).

ACST to GMT

-9h 30m

ACST

ACSTSOURCE

UTC+09:30DST observed

HH12

MM00

12:00 (24-hr)

12 AM6 AM12 PM6 PM12 AM

GMT

UTC+01:00☀ DST active

HH02

MM30

02:30 (24-hr)

12 AM6 AM12 PM6 PM12 AM

Quick Reference

Time Conversion Table

ACST

GMT

12:00 AM

3:30 PM-1

2:00 AM

5:30 PM-1

4:00 AM

7:30 PM-1

6:00 AM

9:30 PM-1

8:00 AM

11:30 PM-1

10:00 AM

1:30 AM

12:00 PM

3:30 AM

2:00 PM

5:30 AM

4:00 PM

7:30 AM

6:00 PM

9:30 AM

8:00 PM

11:30 AM

10:00 PM

1:30 PM

Green rows indicate typical business hours (9 AM - 5 PM)

ACST and GMT on the World Map

The map below highlights the ACST (Australian Central Standard Time) and GMT (Greenwich Mean Time) timezone regions across the globe.

ACST Zone

→

GMT Zone

Explore all world timezones interactively →

ACST – Australian Central Standard Time

UTC+09:30

Australian Central Standard Time (ACST, UTC+09:30) covers South Australia and the Northern Territory, on a half-hour offset.

Countries in ACST

Australia (South Australia, Northern Territory)

Major Cities in ACST

AdelaideDarwinAlice SpringsMount Gambier

Key Facts about ACST

•ACST uses a half-hour offset: UTC+09:30.
•South Australia moves to ACDT (UTC+10:30) in summer; the Northern Territory does not.
•Adelaide and Darwin are 30 minutes apart during daylight saving, level in winter.
•Adelaide is one of the few major cities on a 30-minute offset.

Daylight Saving:Yes – switches to ACDT

Learn more about ACST on Wikipedia

GMT – Greenwich Mean Time

UTC+00:00

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London. It is the same as UTC+00:00.

Countries in GMT

United KingdomIrelandIcelandPortugal (mainland)GhanaSenegalMaliMauritaniaGambiaGuineaSierra LeoneLiberiaIvory CoastBurkina FasoMorocco (historically)

Major Cities in GMT

LondonDublinLisbonAccraReykjavikEdinburghCasablancaDakarBamakoAbidjanConakryFreetownMonrovia

Key Facts about GMT

•GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London.
•The Royal Observatory in Greenwich has been the reference point for GMT since 1884.
•GMT and UTC are often used interchangeably, but UTC is based on atomic clocks.
•Iceland uses GMT year-round and never observes daylight saving time.
•The UK switches from GMT to BST (British Summer Time) in late March each year.

Daylight Saving:Yes – switches to BST

Learn more about GMT on Wikipedia

Everything You Need to Know About ACST and GMT Time

ACST runs on Australian Central Standard Time (ACST) at UTC+09:30. GMT runs on Greenwich Mean Time (GMT) at UTC+00:00. That puts ACST 9 hours 30 minutes behind GMT — a difference of -9h 30m at the current offsets.

In practice, when it is 9:00 AM in ACST it is 11:30 PM in GMT on the previous day. Midnight in ACST is 2:30 PM in GMT. Neither zone observes daylight saving time, so the offset between them stays constant all year.

ACST to GMT time conversion table

ACST (ACST)	GMT (GMT)	Day
12:00 AM	2:30 PM	previous day
6:00 AM	8:30 PM	previous day
7:00 AM	9:30 PM	previous day
8:00 AM	10:30 PM	previous day
9:00 AM	11:30 PM	previous day
12:00 PM	2:30 AM	same day
3:00 PM	5:30 AM	same day
5:00 PM	7:30 AM	same day
6:00 PM	8:30 AM	same day
9:00 PM	11:30 AM	same day

Why people convert ACST to GMT time

Scheduling a call from ACST to GMT: a 10:00 AM start in ACST lands at 12:30 AM in GMT, so you can confirm the slot without doing the arithmetic yourself.
Handling a -9h 30m gap: ACST and GMT have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in GMT is 11:30 PM in ACST.
Keeping family and friends in sync: knowing that 8:00 PM in ACST is 10:30 AM in GMT makes it easy to avoid calling at 3 AM.

Always state the zone abbreviation, not just the hour. "3:00 PM ACST" is unambiguous; "3 PM" across a -9h 30m gap is not.
With a -9h 30m gap there is no shared 9-to-5 window, so alternate the early start: one week ACST takes the early slot, the next week GMT does.

About ACST (Australian Central Standard Time)

Australian Central Standard Time (ACST) is the half-hour offset of UTC+09:30 used across South Australia and the Northern Territory, taking in Adelaide and Darwin. South Australia moves to Australian Central Daylight Time (ACDT, UTC+10:30) from the first Sunday in October to the first Sunday in April, but the Northern Territory does not observe daylight saving — so Adelaide and Darwin sit 30 minutes apart in summer and level with each other in winter. The half-hour offset means Adelaide is 30 minutes behind Sydney in winter and level with it during daylight saving, which regularly catches out travellers and meeting planners.

About GMT (Greenwich Mean Time)

Greenwich Mean Time (GMT) is the clock time at the Royal Observatory in Greenwich, London, which sits on the Prime Meridian (0° longitude). GMT serves as the reference point from which all other time zones are calculated. The United Kingdom uses GMT during winter months and switches to British Summer Time (BST, UTC+01:00) from late March to late October. Several West African nations use GMT year-round. GMT is often used interchangeably with UTC (Coordinated Universal Time), although technically they are different – UTC is based on atomic clocks while GMT is based on Earth's rotation.

Best time to call between ACST and GMT

With a -9h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. GMT opens at 9:00 AM GMT, which is 11:30 PM in ACST, so real-time calls need an early-morning or late-evening slot on one side.

Business hours overlap

ACST and GMT have no shared working hours because of the -9h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.

ACST is 9 hours 30 minutes behind GMT (ACST UTC+09:30 → GMT UTC+00:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.

🕐 Daylight Saving Time Info

ACST

❄ Currently in Standard Time

Standard: UTC+09:30 · DST: UTC+10:30

Clocks spring forward on Sat, Oct 3, 2026

GMT

☀ Currently in DST

Standard: UTC+00:00 · DST: UTC+01:00

Clocks fall back on Sun, Oct 25, 2026

⚠ These locations are currently in different DST states, so the time difference may change when clocks adjust.

Learn More About Time

Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:

⏳

History of Timekeeping

From sundials to atomic clocks - 5000 years of measuring time

🌍

How Time Zones Work

UTC, offsets, and why zones don't follow straight lines

☀️

Daylight Saving Time

DST dates, which countries observe it, and the ongoing debate

Frequently Asked Questions

What is the time difference between ACST and GMT?

ACST (ACST, UTC+09:30) is 9 hours 30 minutes behind GMT (GMT, UTC+00:00). The gap is currently -9h 30m.

How do I convert ACST time to GMT time?

Add -9h 30m to ACST local time. For example, 9:00 AM in ACST is 11:30 PM in GMT (previous day).

What time is it in GMT right now?

GMT uses GMT at UTC+00:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -9h 30m offset from ACST.

What is the best time to call GMT from ACST?

There is no shared working-hours window because of the -9h 30m gap. The closest option is 1:00 PM in ACST, which is 3:30 AM in GMT.

Which is behind, ACST or GMT?

ACST is 9 hours 30 minutes behind GMT. When it is 12:00 PM in ACST it is 2:30 AM in GMT.

Does daylight saving time affect the ACST–GMT difference?

Neither zone observes daylight saving time, so the -9h 30m offset between ACST and GMT is fixed all year.

Which other cities share ACST's time zone?

ACST also covers Adelaide, Darwin, Alice Springs, Mount Gambier.

Which countries use ACST, ACST's zone?

ACST is used in Australia (South Australia, Northern Territory).

Is there a day difference between ACST and GMT?

Not normally. The -9h 30m gap only pushes the date over the previous day.

What is the time difference between ACST and GMT?

GMT is -9h 30m from ACST.

What timezone is ACST in?

ACST operates on its local timezone.

What timezone is GMT in?

GMT operates on its local timezone.

Which countries use ACST (Australian Central Standard Time)?

ACST is used in Australia (South Australia, Northern Territory).

Does ACST observe daylight saving time?

Yes, ACST switches to ACDT during summer months.

What are some interesting facts about ACST?

ACST uses a half-hour offset: UTC+09:30. South Australia moves to ACDT (UTC+10:30) in summer; the Northern Territory does not.

Which cities are in the GMT timezone?

Major cities in the GMT timezone include London, Dublin, Lisbon, Accra, Reykjavik, Edinburgh, Casablanca, Dakar.

What is the UTC offset for GMT?

Greenwich Mean Time (GMT) is at UTC+00:00. During daylight saving time, it shifts to BST.

What should I know about the GMT timezone?

GMT is based on the Prime Meridian (0° longitude) passing through Greenwich, London. The Royal Observatory in Greenwich has been the reference point for GMT since 1884.