IST to GMT Converter

Which IST and which GMT?

Zone abbreviations are ambiguous, so this page starts by pinning both down. IST here is India Standard Time: the IANA zone Asia/Kolkata, anchored on New Delhi. Note that IST is also Irish Standard Time and Israel Standard Time; this page means only the New Delhi sense. GMT here is Greenwich Mean Time: Europe/London, anchored on London. Note that GMT is also UTC±0 kept year-round, which London does not do; this page means only the London sense.

New Delhi keeps UTC+5:30 all year — its January and July offsets are both UTC+5:30 — so IST has no summer-time sibling and never needs disambiguating by season.

GMT in the everyday sense means London time, whichever of GMT or BST (British Summer Time) is in force. London is not on GMT all year: its offset is UTC±0 while standard time applies (its January offset) and UTC+1 while daylight saving is active (its July offset). As of September 2026 it is on BST (UTC+1). Wherever this page writes GMT, read it as "London time on the date in question".

New Delhi's offset is not a whole number of hours, which is why every gap on this page carries minutes as well as hours: the difference between UTC+5:30 and UTC+1 cannot be a round number.

The difference as of September 2026

As of September 2026, London is 4:30 hours behind New Delhi. New Delhi is on UTC+5:30 (no seasonal change) and London is on UTC+1 (BST, daylight saving in effect). Subtract one offset from the other and you have the gap. As wall clocks: 9:00 AM in New Delhi is 4:30 AM in London, 5:00 PM in New Delhi is 12:30 PM in London, and 9:00 AM in London is 1:30 PM in New Delhi.

Next scheduled clock changes: no clock change is scheduled for New Delhi within the next 450 days; clocks in London go back 1 hour on Sunday, October 25, 2026 (local date), moving the offset from UTC+1 to UTC±0. Only London's changes matter to this pair, and each one moves the gap.

How the gap changes through the year

Only one side of this pair changes its clocks. New Delhi keeps UTC+5:30 all year — its January and July offsets are identical — while London moves between UTC±0 (its January offset, GMT) and UTC+1 (its July offset, BST). Every time London shifts, the whole difference shifts with it, because the other offset is standing still. So the gap takes two values a year: London is 5:30 hours behind New Delhi while London is on GMT, and 4:30 hours behind New Delhi while it is on BST.

Over the year scanned from Sep 7, 2026, the engine finds two such moves, each at the exact minute London's clocks change:

• Sunday, October 25, 2026 (London date): the gap goes from 4:30 hours behind to 5:30 hours behind.
• Sunday, March 28, 2027 (London date): the gap goes from 5:30 hours behind to 4:30 hours behind.

The practical consequence is the one that catches recurring meetings. A call fixed at 9:00 AM on New Delhi's clock is 3:30 AM in London while London is on GMT, and 4:30 AM while it is on BST. Nobody in New Delhi sees the meeting move, but on London's calendar it jumps by 1 hour on each of the dates above. The reverse is just as true: a 9:00 AM slot fixed on London's clock lands at 2:30 PM or 1:30 PM in New Delhi depending on the season. Whichever side owns the invitation, the other side sees it move twice a year — which is exactly what the converter above accounts for when you give it a date.

Working hours that overlap

Assume a 9:00 AM to 5:00 PM day on both sides. Because the gap changes during the year, the overlap changes with it, so it is shown for each gap the pair takes:

• London 5:30 hours behind New Delhi (IST / GMT; 154 of the 365 days scanned): 2 hours 30 minutes of shared working time: 2:30 PM to 5:00 PM in New Delhi, which is 9:00 AM to 11:30 AM in London.
• London 4:30 hours behind New Delhi (IST / BST; 211 of the 365 days scanned): 3 hours 30 minutes of shared working time: 1:30 PM to 5:00 PM in New Delhi, which is 9:00 AM to 12:30 PM in London.

The 9-to-5 window is a convention, not a fact about anyone's real hours. The Meeting Planner lets you set each side's actual working hours and shows the overlap for the exact date you are planning.

Converting GMT to IST

This page serves both directions, because the reverse conversion is the same gap with the sign flipped. As of September 2026, New Delhi is 4:30 hours ahead of London, so:

• 9:00 AM IST (New Delhi) = 4:30 AM GMT (London)
• 9:00 AM GMT (London) = 1:30 PM IST (New Delhi)
• 5:00 PM GMT (London) = 9:30 PM IST (New Delhi)

To run GMT to IST in the converter above, swap the From and To menus; the result shows both offsets for the date you enter and flags a day change whenever the reading lands on the previous or next calendar day. The readings above hold only while the gap is 4:30 hours behind; on the dates listed in the section above they move, in both directions at once.

More on these zones

• Current time in New Delhi — live clock, offset and next clock change.
• Current time in London — live clock, offset and next clock change.
• Time Zone Converter — any city to any city, DST-correct for the date.
• Meeting Planner — overlap for your real working hours.
• All zone-to-zone converters — the other corridors on this site.

IST to GMT — frequently asked questions

Conversions are computed locally in your browser from its IANA time zone data; nothing you enter is transmitted. The schedule and offsets on this page were derived from the same database at build time, as of September 2026. Jurisdictions occasionally change DST law with short notice, and the IANA database follows reality — for legally critical timing, confirm against an official source. See the methodology page.