London to New Delhi: the shifting gap
Call at 09:00 UK time on a Tuesday in January and it is 14:30 in New Delhi. Make the same call on a Tuesday in July and it is 13:30. The difference is not a mistake. It is British Summer Time.
India Standard Time stays fixed at UTC+5:30 all year. The UK moves. In winter the UK runs on Greenwich Mean Time. In summer it runs on British Summer Time, one hour ahead. That single hour changes your overlap.
When the UK is on GMT, London is 5.5 hours behind New Delhi. When the UK is on BST, London is 4.5 hours behind.
Why does the UK, India time gap change from 5.5 to 4.5 hours?
India last observed daylight saving in 1971. The clocks do not move. The UK shifts on the last Sunday of March and the last Sunday of October.
- Winter window (late October to late March): UK on GMT. India is 5 hours 30 minutes ahead.
- Summer window (late March to late October): UK on BST. India is 4 hours 30 minutes ahead.
This trips up more callers than any other scheduling detail. Use +5:30 to book a July call and you will be an hour early. The correct summer offset is +4:30.
UK morning to India: the core calling window
Your morning is India’s afternoon. This is the most reliable block for reaching someone at a desk.
| UK time | IST (winter, GMT) | IST (summer, BST) |
|---|---|---|
| 08:00 | 13:30 | 12:30 |
| 09:00 | 14:30 | 13:30 |
| 10:00 | 15:30 | 14:30 |
| 11:00 | 16:30 | 15:30 |
| 12:00 | 17:30 | 16:30 |
Dial at 09:00 UK time and you reach India at 14:30 in winter, 13:30 in summer. Both sit inside standard Indian office hours, which run 09:30 to 18:30 IST. You have a clean window from 08:00 to 12:00 UK time.
UK afternoon to India: a short, risky window
Your afternoon is India’s evening. The usable overlap shrinks fast.
In winter, 13:00 UK is 18:30 IST. That is the hard stop of the Indian work day. In summer, 13:00 UK is 17:30 IST. You have roughly one hour left.
Push past 14:00 UK in winter and India is beyond 19:30. Past 14:30 UK in summer, same result. Offices are closed. Call after that and you are dialling a personal number, not a desk.
What is the best time to call India from the UK in winter vs summer?
Indian offices typically operate 09:30 to 18:30 IST. UK offices run 09:00 to 17:00.
- Winter: 09:00 to 12:00 UK equals 14:30 to 17:30 IST. A three-hour overlap.
- Summer: 09:00 to 12:00 UK equals 13:30 to 16:30 IST. The same three hours, shifted one hour earlier in India.
The overlap length is identical. What changes is the lunch break. Many Indian offices break between 13:00 and 14:00 IST. In summer, a 09:00 UK call lands at 13:30 IST, dead in the middle of lunch. Push to 10:00 UK (14:30 IST) and you clear it.
The BST trap: why 4.5 hours catches people out
When the UK enters BST, the offset to India contracts from 5.5 hours to 4.5 hours.
A meeting booked for 10:00 UK in January happens at 15:30 IST. The same meeting booked for 10:00 UK in July happens at 14:30 IST. If your calendar tool resolves time zones poorly, you show up an hour early or an hour late.
Check the Indian time on the invitation, not just your own. Use a converter that accounts for the UK’s daylight saving. The India to UK Time, IST vs GMT / BST page shows the exact current gap.
Tape this rule to your monitor: UK on BST, add 4.5 hours. UK on GMT, add 5.5 hours.
How to call India from the UK without a missed connection
Dial before noon UK time. Before 12:00 UK keeps you inside Indian working hours in both seasons.
Skip UK late afternoons. After 14:00 UK in winter, India is past 19:30. After 14:30 UK in summer, same cutoff. You are calling after hours.
Work around the Indian lunch break. Lunch runs roughly 13:00 to 14:00 IST. In summer, a 09:00 UK call hits at 13:30 IST. If you need a decision-maker, call at 10:00 UK instead.
Dial the country code correctly. India’s code is +91. From a UK line, dial 00 91, then the local number. Drop the leading zero from the Indian area code.
Check Indian holidays before you send the invite. India observes public holidays the UK does not share. Republic Day on Monday 26 January 2026, Independence Day on Saturday 15 August 2026, Diwali on Sunday 8 November 2026, and Holi on Wednesday 4 March 2026 all shut government offices and many businesses. A full list is on the Indian Business Hours and Holidays page.
Verify the offset with a converter that handles BST. Do not trust a phone world clock without checking. The IST Converter shows the current time in both zones and adjusts for BST automatically.
Best time to call friends or night-shift contacts in India
Calling family or friends? Ignore business hours. Indian dinner is typically 19:30 to 22:00 IST. That is 14:00 to 17:30 UK in winter and 15:00 to 18:30 UK in summer. A solid window for a personal call.
Calling someone in India’s IT or BPO sector? The standard advice shifts. Many teams work night shifts to overlap with US hours. A call at 17:00 UK time might catch someone mid-shift. Ask your contact for their actual working hours. Do not assume 09:30 to 18:30.