Convert GMT to ACST
ACST is 9 hours 30 minutes ahead of GMT. GMT is UTC+0 and ACST is UTC+9:30.
Right now: GMT · ACST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between GMT and ACST. Someone has to take an early or late call — or use asynchronous communication instead.
| GMT | ACST | Suitable? |
|---|---|---|
| 9:00 AM | 6:30 PM | outside 9–5 |
| 10:00 AM | 7:30 PM | outside 9–5 |
| 11:00 AM | 8:30 PM | outside 9–5 |
| 12:00 PM | 9:30 PM | outside 9–5 |
| 1:00 PM | 10:30 PM | outside 9–5 |
| 2:00 PM | 11:30 PM | outside 9–5 |
| 3:00 PM | 12:30 AM (next day) | outside 9–5 |
| 4:00 PM | 1:30 AM (next day) | outside 9–5 |
| 5:00 PM | 2:30 AM (next day) | outside 9–5 |
GMT to ACST conversion table
| GMT | ACST |
|---|---|
| 12:00 AM | 9:30 AM |
| 1:00 AM | 10:30 AM |
| 2:00 AM | 11:30 AM |
| 3:00 AM | 12:30 PM |
| 4:00 AM | 1:30 PM |
| 5:00 AM | 2:30 PM |
| 6:00 AM | 3:30 PM |
| 7:00 AM | 4:30 PM |
| 8:00 AM | 5:30 PM |
| 9:00 AM | 6:30 PM |
| 10:00 AM | 7:30 PM |
| 11:00 AM | 8:30 PM |
| 12:00 PM | 9:30 PM |
| 1:00 PM | 10:30 PM |
| 2:00 PM | 11:30 PM |
| 3:00 PM | 12:30 AM (next day) |
| 4:00 PM | 1:30 AM (next day) |
| 5:00 PM | 2:30 AM (next day) |
| 6:00 PM | 3:30 AM (next day) |
| 7:00 PM | 4:30 AM (next day) |
| 8:00 PM | 5:30 AM (next day) |
| 9:00 PM | 6:30 AM (next day) |
| 10:00 PM | 7:30 AM (next day) |
| 11:00 PM | 8:30 AM (next day) |
About GMT
Greenwich Mean Time (GMT) is UTC+0. It is used in the UK and Ireland in winter, Portugal, Iceland and much of West Africa.
The trap with GMT is that the United Kingdom is not on it for most of the year. From late March to late October the UK runs BST, UTC+1, so a meeting agreed "10am GMT" with a London colleague in July is an hour out unless both parties meant the abbreviation literally. Broadcasters and airlines avoid the ambiguity by saying UTC. GMT itself is fixed at UTC+0 and does not shift; it is the UK's clocks that move away from it and back.
About ACST
Australian Central Standard Time (ACST) is UTC+9:30. It is used in Adelaide and Darwin in winter.
Australian Central Standard Time is UTC+9:30, half an hour behind the eastern states rather than a whole hour, which surprises people every time. South Australia moves to daylight saving in October and the Northern Territory does not, so Adelaide and Darwin share this offset for half the year and are an hour apart for the other half.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on GMT switches to BST (UTC+1) from late March to late October. So the 9.5-hour figure on this page is correct for the part of the year when both places are actually on these abbreviations, and changes by an hour outside it.
ACST does not shift, so the whole change comes from one side. A recurring meeting fixed in ACST will appear to move by an hour for everyone on the other side, twice a year, without anyone changing anything.
This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.
Frequently asked questions
What time is 9:00 AM GMT in ACST?
9:00 AM GMT is 6:30 PM ACST.
Is ACST ahead of GMT?
ACST is 9 hours 30 minutes ahead of GMT.
Which time zone does this use?
GMT is UTC+0 and ACST is UTC+9:30. Both abbreviations denote a single fixed offset, so this conversion never shifts with daylight saving — what changes is which abbreviation a place is using at the time.