GMT vs IST time zone comparison

How GMT and IST compare

India Standard Time runs five hours and thirty minutes ahead of Greenwich Mean Time, one of the few major time zones with a half-hour offset. London-to-India coordination is a defining axis of modern global business: Bangalore, Hyderabad, Pune, Mumbai, and Delhi together host the world's largest concentration of software engineering, business process outsourcing, and back-office finance. The five-and-a-half-hour gap is wide enough to be inconvenient but narrow enough to permit overlap during business hours, which is exactly why so much development work flows between London and Bangalore. The classic overlap window is 1 PM GMT to 4 PM GMT, which is 6:30 PM IST to 9:30 PM IST. That is the late evening in India, when many engineering teams are still at the office or working from home for end-of-day handoffs. Push the call later than 4 PM London (9:30 PM IST) and you are asking the India side to give up dinner. Push it earlier than 1 PM London (6:30 PM IST) and the India side is still mid-day in their own working session. The half-hour offset trips up calendar tools that round to the nearest hour; double-check converted times before sending invites.

Working-hour overlap

Functional overlap from 1 PM to 5 PM London (6:30 PM to 10:30 PM IST), with 2 PM London the realistic default before fatigue sets in on the India side.

When to schedule

Default to 2 PM London (7:30 PM IST) for cross-zone meetings. This is past lunch in London and the late-afternoon stretch in India, and most engineering teams treat 7-9 PM IST as legitimate work hours for client coordination. For follow-the-sun handoffs, the India side typically writes a summary at end-of-day India (around 6:30 PM IST, which is 1 PM London) and the London team picks it up after lunch. For one-off urgent calls, 4 PM London (9:30 PM IST) is workable but tight. Avoid recurring weekly meetings later than 5 PM London (10:30 PM IST) — they degrade attendance fast.

Notable context

Bangalore is the world's second-largest IT services hub by employment after Silicon Valley, and the UK is one of its largest customer bases. The big four Indian IT services firms (TCS, Infosys, Wipro, HCL) all run dedicated UK-hour shift teams, where Indian engineers explicitly work UK business hours for a premium. India does not observe daylight saving, so the gap to London shifts from 5h30 in UK winter to 4h30 in UK summer (when the UK is on BST). This means the same 2 PM London standing meeting becomes a 6:30 PM IST call in winter and a 6:30 PM IST call in summer — wait, no: 2 PM BST is 6:30 PM IST too. The half-hour offset is preserved; the absolute IST time of a 2 PM London call does shift by an hour seasonally relative to UTC, but stays at 6:30 PM India because London moves with it.