Convert BST to ACDT
ACDT is 9 hours 30 minutes ahead of BST. BST is UTC+1 and ACDT is UTC+10:30.
Right now: BST · ACDT
Which BST is this?
BST names more than one zone. This page reads it as British Summer Time at UTC+1, which is the reading most converters take. There is one other: Bangladesh Standard Time at UTC+6, used in Bangladesh, all year.
The letters on a meeting invitation do not say which one is meant. If yours is not British Summer Time, the answer above is wrong, and not by a little:
| If BST means | Then |
|---|---|
| British Summer Time — assumed on this page | ACDT is 9.5 hours ahead of BST |
| Bangladesh Standard Time | ACDT is 4.5 hours ahead of BST |
The large converter sites disagree about this as well: search for a BST 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 BST and ACDT. Someone has to take an early or late call — or use asynchronous communication instead.
| BST | ACDT | 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 |
BST to ACDT conversion table
| BST | ACDT |
|---|---|
| 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 BST
British Summer Time (BST) is UTC+1. It is used in the UK from late March to late October.
British Summer Time is UTC+1, in force in the UK and Ireland from the last Sunday in March to the last Sunday in October. The abbreviation is ambiguous: BST also means Bangladesh Standard Time, UTC+6, five hours away. Within the UK it is the reason "GMT" is wrong for most of the year — the clocks are on BST from spring to autumn, and only the winter half of the year is actually GMT.
About ACDT
Australian Central Daylight Time (ACDT) is UTC+10:30. It is used in Adelaide in summer.
Australian Central Daylight Time is UTC+10:30, what South Australia keeps from October to April. Darwin stays on ACST through the summer, so for those months two cities in the same nominal zone are an hour apart — the only reason to be precise about which of the two abbreviations a meeting invitation carries.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on BST switches to GMT (UTC+0) from late October to late March. 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.
ACDT does not shift, so the whole change comes from one side. A recurring meeting fixed in ACDT 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 BST in ACDT?
9:00 AM BST is 6:30 PM ACDT.
Is ACDT ahead of BST?
ACDT is 9 hours 30 minutes ahead of BST.
Which time zone does this use?
BST is UTC+1 and ACDT is UTC+10:30. 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.