Convert IST to ACDT
ACDT is 5 hours ahead of IST. IST is UTC+5:30 and ACDT is UTC+10:30.
Right now: IST · ACDT
Which IST is this?
IST names more than one zone. This page reads it as India Standard Time at UTC+5:30, which is the reading most converters take. There are others: Israel Standard Time at UTC+2, used in Israel in winter; Irish Standard Time at UTC+1, used in Ireland in summer.
The letters on a meeting invitation do not say which one is meant. If yours is not India Standard Time, the answer above is wrong, and not by a little:
| If IST means | Then |
|---|---|
| India Standard Time — assumed on this page | ACDT is 5 hours ahead of IST |
| Israel Standard Time | ACDT is 8.5 hours ahead of IST |
| Irish Standard Time | ACDT is 9.5 hours ahead of IST |
The large converter sites disagree about this as well: search for a IST 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 overlap for 3 hours: 9:00 AM–12:00 PM IST (2:00 PM–5:00 PM ACDT). Schedule meetings inside that window.
| IST | ACDT | Suitable? |
|---|---|---|
| 9:00 AM | 2:00 PM | working hours |
| 10:00 AM | 3:00 PM | working hours |
| 11:00 AM | 4:00 PM | working hours |
| 12:00 PM | 5:00 PM | outside 9–5 |
| 1:00 PM | 6:00 PM | outside 9–5 |
| 2:00 PM | 7:00 PM | outside 9–5 |
| 3:00 PM | 8:00 PM | outside 9–5 |
| 4:00 PM | 9:00 PM | outside 9–5 |
| 5:00 PM | 10:00 PM | outside 9–5 |
IST to ACDT conversion table
| IST | ACDT |
|---|---|
| 12:00 AM | 5:00 AM |
| 1:00 AM | 6:00 AM |
| 2:00 AM | 7:00 AM |
| 3:00 AM | 8:00 AM |
| 4:00 AM | 9:00 AM |
| 5:00 AM | 10:00 AM |
| 6:00 AM | 11:00 AM |
| 7:00 AM | 12:00 PM |
| 8:00 AM | 1:00 PM |
| 9:00 AM | 2:00 PM |
| 10:00 AM | 3:00 PM |
| 11:00 AM | 4:00 PM |
| 12:00 PM | 5:00 PM |
| 1:00 PM | 6:00 PM |
| 2:00 PM | 7:00 PM |
| 3:00 PM | 8:00 PM |
| 4:00 PM | 9:00 PM |
| 5:00 PM | 10:00 PM |
| 6:00 PM | 11:00 PM |
| 7:00 PM | 12:00 AM (next day) |
| 8:00 PM | 1:00 AM (next day) |
| 9:00 PM | 2:00 AM (next day) |
| 10:00 PM | 3:00 AM (next day) |
| 11:00 PM | 4:00 AM (next day) |
About IST
India Standard Time (IST) is UTC+5:30. It is used in all of India and Sri Lanka, on a half-hour offset.
India Standard Time is UTC+5:30 — one of the handful of zones offset by half an hour, which breaks any code that assumes whole-hour offsets and any mental arithmetic that does the same. India has no daylight saving and one time zone for the entire country, despite spanning nearly 30 degrees of longitude. The abbreviation is also used for Irish Standard Time and Israel Standard Time, both of which are entirely different offsets.
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?
Neither IST nor ACDT shifts with the seasons, so this 5-hour difference holds all year. That is unusual enough to be worth relying on: most cross-continental gaps move twice a year.
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 IST in ACDT?
9:00 AM IST is 2:00 PM ACDT.
Is ACDT ahead of IST?
ACDT is 5 hours ahead of IST.
Which time zone does this use?
IST is UTC+5:30 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.