There is no overlap between 09:00–18:00 working days in these two places.
How many hours is IST ahead of HDT?
As abbreviations, HDT is always 14.5 hours behind of IST: IST is UTC+5:30 and HDT is UTC−9. To convert, subtract 14.5 hours.
When the IST to HDT time difference changes
For most of the year HDT is 14.5 hours behind of IST. From 1 November to 31 December 2026, HDT is 15.5 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
HDT vs IST
Length
8 March 2026 to 31 October 2026
14.5 hours behind
238 days
1 November 2026 to 31 December 2026
15.5 hours behind
61 days
1 January 2027 to 13 March 2027
15.5 hours behind
72 days
14 March 2027 to 6 November 2027
14.5 hours behind
238 days
7 November 2027 to 31 December 2027
15.5 hours behind
55 days
Best time for a meeting between IST and HDT
When HDT is 14.5 hours behind of IST: no shared 09:00 to 17:00 hours; one side has to take the call outside office hours.
When HDT is 15.5 hours behind of IST: no shared 09:00 to 17:00 hours; one side has to take the call outside office hours.
Frequently asked questions about IST and HDT time
How many hours ahead is HDT of IST?
HDT (UTC−9) is 14.5 hours behind of IST (UTC+5:30).
Does the time difference between IST and HDT change?
Yes. It is usually 14.5 hours behind, but changes when one side moves its clocks: 15.5 hours behind from 1 November to 31 December 2026; 15.5 hours behind from 1 January to 13 March 2027.