There is no overlap between 09:00–18:00 working days in these two places.
How many hours is IST ahead of ADT?
As abbreviations, ADT is always 8.5 hours behind of IST: IST is UTC+5:30 and ADT is UTC−3. To convert, subtract 8.5 hours.
When the IST to ADT time difference changes
For most of the year ADT is 8.5 hours behind of IST. From 1 November to 31 December 2026, ADT is 9.5 hours behind of IST instead, because the two places change their clocks on different dates. Meetings booked by the usual gap land an hour off in those weeks.
Dates
ADT vs IST
Length
8 March 2026 to 31 October 2026
8.5 hours behind
238 days
1 November 2026 to 31 December 2026
9.5 hours behind
61 days
1 January 2027 to 13 March 2027
9.5 hours behind
72 days
14 March 2027 to 6 November 2027
8.5 hours behind
238 days
7 November 2027 to 31 December 2027
9.5 hours behind
55 days
Calling hours for IST and ADT
When ADT is 8.5 hours behind of IST: no shared 09:00 to 17:00 hours; try 17:00 in IST (08:30 in ADT).
When ADT is 9.5 hours behind of IST: no shared 09:00 to 17:00 hours; try 17:00 in IST (07:30 in ADT).
Frequently asked questions about IST and ADT time
How many hours ahead is ADT of IST?
ADT (UTC−3) is 8.5 hours behind of IST (UTC+5:30).
Does the time difference between IST and ADT change?
Yes. It is usually 8.5 hours behind, but changes when one side moves its clocks: 9.5 hours behind from 1 November to 31 December 2026; 9.5 hours behind from 1 January to 13 March 2027.