How many hours ahead is IST compared to GMT?

India Standard Time (IST, UTC+5:30) is 5 hours and 30 minutes ahead of GMT (UTC+0) year-round. In summer when the UK switches to BST (UTC+1), IST is only 4 hours and 30 minutes ahead of British local time. India never observes daylight saving time, so any change in the gap is caused by the UK’s clock change.

What is the best time to schedule a call between India and London?

The most comfortable window is afternoon India time / morning UK time. A call at 2:30–4:30 PM IST is 9 AM–11 AM GMT (winter) or 9 AM–11 AM BST (summer, with IST at 1:30–3:30 PM). This catches India after lunch and the UK in a fresh morning slot. Both sides are in comfortable working hours.

Why does IST have a half-hour offset from GMT?

India chose UTC+5:30 to create a single nationwide time zone that splits the difference across the country’s 30-degree longitude span. The half-hour offset minimizes the solar noon deviation for the most populated parts of the country. It is not aligned to any whole-hour UTC zone, which creates the fractional gaps that surprise schedulers.

IST vs GMT: Time Difference and Conversion

March 24, 2026

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Frequently Asked Questions

How many hours ahead is IST compared to GMT?: India Standard Time (IST, UTC+5:30) is 5 hours and 30 minutes ahead of GMT (UTC+0) year-round. In summer when the UK switches to BST (UTC+1), IST is only 4 hours and 30 minutes ahead of British local time. India never observes daylight saving time, so any change in the gap is caused by the UK’s clock change.
What is the best time to schedule a call between India and London?: The most comfortable window is afternoon India time / morning UK time. A call at 2:30–4:30 PM IST is 9 AM–11 AM GMT (winter) or 9 AM–11 AM BST (summer, with IST at 1:30–3:30 PM). This catches India after lunch and the UK in a fresh morning slot. Both sides are in comfortable working hours.
Why does IST have a half-hour offset from GMT?: India chose UTC+5:30 to create a single nationwide time zone that splits the difference across the country’s 30-degree longitude span. The half-hour offset minimizes the solar noon deviation for the most populated parts of the country. It is not aligned to any whole-hour UTC zone, which creates the fractional gaps that surprise schedulers.