IST to AEST
Convert India Standard Time (IST) to Australian Eastern Time (AEST/AEDT) and back. Right now Sydney is 5 hours 30 minutes ahead of Kolkata. Daylight saving is applied for the date being converted, not for today.
| Zone | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | Copy |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Kolkata | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | |
| Sydney | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 00 +1d | 01 +1d | 02 +1d | 03 +1d | 04 +1d | |
| UTC | 18 -1d | 19 -1d | 20 -1d | 21 -1d | 22 -1d | 23 -1d | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | |
09–17 working hours 07–09 shoulder 23–06 night Hover an hour to convert it · click to pin it, then copy any row
How far apart Kolkata and Sydney really are
The difference between these two zones is not a single number. Across 2026 it takes 2 different values — 4 hours 30 minutes, 5 hours 30 minutes — because Sydney observes daylight saving and Kolkata does not.
| Period in 2026 | Sydney is |
|---|---|
| 1 Jan – 4 Apr | 5 hours 30 minutes ahead of Kolkata |
| 5 Apr – 3 Oct | 4 hours 30 minutes ahead of Kolkata |
| 4 Oct – 31 Dec | 5 hours 30 minutes ahead of Kolkata |
Working-hours overlap
Treating 09:00–17:00 as the working day in both places, there are 3 hours of overlap: 9:00 am, 10:00 am, 11:00 am in Kolkata, which is 2:30 pm, 3:30 pm, 4:30 pm in Sydney. Those are the slots to aim for; everything else costs someone their evening.
Kolkata to Sydney, hour by hour
Every hour of Kolkata's day and the matching local time in Sydney, for 22 Oct 2026. Rows where both cities are inside working hours are marked.
| Kolkata (IST) | Sydney (AEST) | Both working? |
|---|---|---|
| 12:00 am | 5:30 am | — |
| 1:00 am | 6:30 am | — |
| 2:00 am | 7:30 am | — |
| 3:00 am | 8:30 am | — |
| 4:00 am | 9:30 am | — |
| 5:00 am | 10:30 am | — |
| 6:00 am | 11:30 am | — |
| 7:00 am | 12:30 pm | — |
| 8:00 am | 1:30 pm | — |
| 9:00 am | 2:30 pm | Yes |
| 10:00 am | 3:30 pm | Yes |
| 11:00 am | 4:30 pm | Yes |
| 12:00 pm | 5:30 pm | — |
| 1:00 pm | 6:30 pm | — |
| 2:00 pm | 7:30 pm | — |
| 3:00 pm | 8:30 pm | — |
| 4:00 pm | 9:30 pm | — |
| 5:00 pm | 10:30 pm | — |
| 6:00 pm | 11:30 pm | — |
| 7:00 pm | 12:30 am next day | — |
| 8:00 pm | 1:30 am next day | — |
| 9:00 pm | 2:30 am next day | — |
| 10:00 pm | 3:30 am next day | — |
| 11:00 pm | 4:30 am next day | — |
Why you should store the zone, not the offset
Because the gap between Kolkata and Sydney changes during the year, an offset recorded as a number is only correct until the next transition. Store Asia/Kolkata and Australia/Sydney — the IANA
identifiers — alongside any time a user entered locally. The identifier
carries the zone's entire history of rule changes, so a date from 1995
converts with the rules that were in force in 1995.
Internally, keep the instant as a Unix timestamp. The epoch value is identical in Kolkata, Sydney and everywhere else; the zone is applied only at the edges, when a human needs to read it. The current Unix timestamp is at the top of this page, and the zones versus offsets guide explains why the distinction bites.
Related conversions
Frequently asked questions
What time is it in Sydney when it is 9:00 am in Kolkata?
9:00 am IST is 2:30 pm in Sydney. The full hour-by-hour table on this page covers every other hour of the day.
How many hours ahead is AEST of IST?
Right now Sydney is 5 hours 30 minutes ahead of Kolkata. The gap is not fixed: across 2026 it takes 2 different values — 4 hours 30 minutes, 5 hours 30 minutes — because Sydney observes daylight saving and Kolkata does not.
Is AEST to IST the same conversion in reverse?
Yes — subtract instead of add. If Sydney is 5 hours 30 minutes ahead of Kolkata, then Kolkata is the same interval behind Sydney. The grid on this page reads in both directions, which is why /aest-to-ist leads here rather than to a separate page.
When can Kolkata and Sydney meet during working hours?
There are 3 hours when both cities are inside 09:00–17:00: 9:00 am IST, 10:00 am IST, 11:00 am IST. The green cells in the grid above show the same thing visually.
Does Kolkata or Sydney observe daylight saving time?
Kolkata does not — it stays on UTC+05:30 all year. Sydney does: in 2026 it moves to +11:00 and back to +10:00.