IST to ACST Time Converter

Common Times Converted

IST on the left, ACST on the right.

IST to ACST: Full 24-Hour Conversion Table

Shaded rows are working hours; the darker shade marks the hours when both zones are at work.

What IST and ACST 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.

ACST — Australian Central Standard Time

Adelaide and Darwin. Standing at UTC+9:30 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, April 4, 2027, to ACST. Adelaide moves to ACDT (UTC+10:30) in the southern summer; Darwin never changes.

The Central Australian half-hour offset dates from a 19th-century compromise between the colonies, and Adelaide observes daylight saving while Darwin, in the same zone, does not.

What This Means in Practice

Expect times on the half hour

Both IST and ACST sit 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

ACST 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, April 4, 2027 unless someone resets it.

Major Cities in Each Zone

Cities on IST

Cities on ACST