Britain runs on two clocks a year — and “GMT” only describes one of them.
The United Kingdom uses GMT (UTC+0) from late October to late March and BST — British Summer Time (UTC+1) for the rest of the year. Clocks change on the last Sunday of March and the last Sunday of October at 1 AM.
Saying “GMT” in July when you mean London time. In summer, London is an hour ahead of GMT. If a colleague schedules “3 PM GMT” in June and means local London time, that’s actually 3 PM BST — 2 PM GMT. When precision matters, name the city or use UTC. More: GMT vs UTC.
| City | vs UK winter (GMT) | vs UK summer (BST) |
|---|---|---|
| New York | -5 | -5 |
| India | +5:30 | +4:30 |
| Dubai | +4 | +3 |
| Sydney | +11 | +9 |
The New York gap stays 5 hours nearly all year because the US and UK both observe DST — but their change dates differ. The US springs forward in early March while the UK waits until late March, and the UK falls back in late October while the US waits until early November. During both short mismatch windows the gap temporarily shrinks to 4 hours — worth double-checking any transatlantic meetings in mid-to-late March and the last week of October.
India is 4:30–5:30 ahead of the UK — one of the friendlier business overlaps: a 10 AM London call is mid-afternoon in India. Convert precisely with London to India time or check the live London clock.
The UK is on BST (UTC+1) from the last Sunday of March to the last Sunday of October, and GMT (UTC+0) the rest of the year. In summer, it is BST.
India is 5 hours 30 minutes ahead of the UK during GMT (winter) and 4 hours 30 minutes ahead during BST (summer).
On the last Sunday of March (forward one hour) and the last Sunday of October (back one hour), at 1 AM.