Convert ACST to CST
CST is 15 hours 30 minutes behind ACST. ACST is UTC+9:30 and CST is UTC−6.
Right now: ACST · CST
Which CST is this?
CST names more than one zone. This page reads it as Central Standard Time at UTC−6, which is the reading most converters take. There are others: China Standard Time at UTC+8, used in all of mainland China, all year; Cuba Standard Time at UTC−5, used in Cuba in winter.
The letters on a meeting invitation do not say which one is meant. If yours is not Central Standard Time, the answer above is wrong, and not by a little:
| If CST means | Then |
|---|---|
| Central Standard Time — assumed on this page | CST is 15.5 hours behind ACST |
| China Standard Time | CST is 1.5 hours behind ACST |
| Cuba Standard Time | CST is 14.5 hours behind ACST |
The large converter sites disagree about this as well: search for a CST conversion and some of the results answer for one reading and some for another, none of them saying which they chose. Where it matters, ask which country the sender is in rather than which letters they typed.
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between ACST and CST. Someone has to take an early or late call — or use asynchronous communication instead.
| ACST | CST | Suitable? |
|---|---|---|
| 9:00 AM | 5:30 PM (previous day) | outside 9–5 |
| 10:00 AM | 6:30 PM (previous day) | outside 9–5 |
| 11:00 AM | 7:30 PM (previous day) | outside 9–5 |
| 12:00 PM | 8:30 PM (previous day) | outside 9–5 |
| 1:00 PM | 9:30 PM (previous day) | outside 9–5 |
| 2:00 PM | 10:30 PM (previous day) | outside 9–5 |
| 3:00 PM | 11:30 PM (previous day) | outside 9–5 |
| 4:00 PM | 12:30 AM | outside 9–5 |
| 5:00 PM | 1:30 AM | outside 9–5 |
ACST to CST conversion table
| ACST | CST |
|---|---|
| 12:00 AM | 8:30 AM (previous day) |
| 1:00 AM | 9:30 AM (previous day) |
| 2:00 AM | 10:30 AM (previous day) |
| 3:00 AM | 11:30 AM (previous day) |
| 4:00 AM | 12:30 PM (previous day) |
| 5:00 AM | 1:30 PM (previous day) |
| 6:00 AM | 2:30 PM (previous day) |
| 7:00 AM | 3:30 PM (previous day) |
| 8:00 AM | 4:30 PM (previous day) |
| 9:00 AM | 5:30 PM (previous day) |
| 10:00 AM | 6:30 PM (previous day) |
| 11:00 AM | 7:30 PM (previous day) |
| 12:00 PM | 8:30 PM (previous day) |
| 1:00 PM | 9:30 PM (previous day) |
| 2:00 PM | 10:30 PM (previous day) |
| 3:00 PM | 11:30 PM (previous day) |
| 4:00 PM | 12:30 AM |
| 5:00 PM | 1:30 AM |
| 6:00 PM | 2:30 AM |
| 7:00 PM | 3:30 AM |
| 8:00 PM | 4:30 AM |
| 9:00 PM | 5:30 AM |
| 10:00 PM | 6:30 AM |
| 11:00 PM | 7:30 AM |
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.
About CST
Central Standard Time (CST) is UTC−6. It is used in Chicago, Dallas, Houston and Mexico City in winter.
CST is the most overloaded abbreviation in timekeeping. It means US Central Standard Time at UTC−6, China Standard Time at UTC+8, and Cuba Standard Time at UTC−5 — a fourteen-hour spread between the first two. This page uses the North American meaning. If an abbreviation reached you without a country attached, that is a reason to ask rather than to assume, and it is the strongest single argument for storing an IANA zone name such as America/Chicago instead.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on CST switches to CDT (UTC−5) from March to November. So the 15.5-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 ACST in CST?
9:00 AM ACST is 5:30 PM CST (previous day).
Is CST ahead of ACST?
CST is 15 hours 30 minutes behind ACST.
Which time zone does this use?
ACST is UTC+9:30 and CST is UTC−6. 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.