IST to AST Time Converter
AST is 8 hours and 30 minutes behind IST. IST is UTC+5:30, and Atlantic Canada and the Caribbean are currently on ADT (UTC-3:00).
Best Time to Call Between IST and AST
Standard 9-to-5 hours in these two zones never overlap, so someone has to take the call outside their working day. The most workable window is 4:00 PM to 10:00 PM IST, which is 7:30 AM to 1:30 PM AST.
both at work IST only AST only neither — hours along the strip are IST.
Common Times Converted
IST on the left, AST on the right.
IST to AST: Full 24-Hour Conversion Table
Shaded rows are working hours; the darker shade marks the hours when both zones are at work.
| IST | AST | Working hours |
|---|---|---|
| 12:00 AM | 3:30 PM prev day | AST only |
| 1:00 AM | 4:30 PM prev day | AST only |
| 2:00 AM | 5:30 PM prev day | — |
| 3:00 AM | 6:30 PM prev day | — |
| 4:00 AM | 7:30 PM prev day | — |
| 5:00 AM | 8:30 PM prev day | — |
| 6:00 AM | 9:30 PM prev day | — |
| 7:00 AM | 10:30 PM prev day | — |
| 8:00 AM | 11:30 PM prev day | — |
| 9:00 AM | 12:30 AM | IST only |
| 10:00 AM | 1:30 AM | IST only |
| 11:00 AM | 2:30 AM | IST only |
| 12:00 PM | 3:30 AM | IST only |
| 1:00 PM | 4:30 AM | IST only |
| 2:00 PM | 5:30 AM | IST only |
| 3:00 PM | 6:30 AM | IST only |
| 4:00 PM | 7:30 AM | IST only |
| 5:00 PM | 8:30 AM | — |
| 6:00 PM | 9:30 AM | AST only |
| 7:00 PM | 10:30 AM | AST only |
| 8:00 PM | 11:30 AM | AST only |
| 9:00 PM | 12:30 PM | AST only |
| 10:00 PM | 1:30 PM | AST only |
| 11:00 PM | 2:30 PM | AST only |
What IST and AST Actually Are
IST — India Standard Time
Mumbai, Delhi, Bengaluru, Chennai, Kolkata, Hyderabad — and Colombo. Standing at UTC+5:30 as written, and the region does not change its clocks, so that offset holds all year. IST also stands for Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page covers the Indian one, which is by far the most searched.
India runs a single time zone across a country wide enough for two, which is why sunrise in the north-east can come nearly two hours before Mumbai's. Proposals for a second zone resurface regularly and have never been adopted.
AST — Atlantic Standard Time
Halifax, San Juan, Santo Domingo, Bermuda. Standing at UTC-4:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to AST. AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.
Atlantic Standard Time is the only North American zone whose name is more commonly associated, worldwide, with a completely different zone — Arabia Standard Time.
What This Means in Practice
Expect times on the half hour
IST sits on a 30-minute offset rather than a whole hour, so a round number on one side is never a round number on the other. A 9:00 meeting becomes 30 minutes past the hour, which is exactly the detail calendar invitations get wrong when someone converts in their head.
This gap is not fixed
AST changes its clocks and IST does not, so the difference between them moves by an hour twice a year. A recurring meeting set now will drift for one side from Sunday, November 1, 2026 unless someone resets it.
Major Cities in Each Zone
Cities on IST
Cities on AST
Frequently Asked Questions
What is the time difference between IST and AST?
AST is 8 hours and 30 minutes behind IST. That is the live figure. Taken strictly as written, the gap between IST and AST is 9 hours and 30 minutes — the two differ because at least one of these regions is currently on daylight saving.
What is 9:00 AM IST in AST?
9:00 AM IST is 12:30 AM AST.
What are the best hours to schedule a call between IST and AST?
Standard business hours in these two zones do not overlap at all, so one side has to work outside the 9-to-5. The most workable window is 4:00 PM to 10:00 PM IST, which is 7:30 AM to 1:30 PM AST.
Does the difference between IST and AST change during the year?
Yes. AST observes daylight saving and IST does not, so the gap shifts by an hour at least twice a year. The next clock change is on Sunday, November 1, 2026.
Does IST always mean India Standard Time?
IST also stands for Irish Standard Time (UTC+1) and Israel Standard Time (UTC+2). This page covers the Indian one, which is by far the most searched.
Does AST always mean Atlantic Standard Time?
AST also stands for Arabia Standard Time (UTC+3), used in Saudi Arabia, Iraq and Kuwait.