UTC vs GMT: What Is the Difference?

Short answer: UTC is the modern international reference used to coordinate civil time. GMT is the historical Greenwich time reference and is still used as a practical zero-offset label. India Standard Time is UTC+5:30.

UTC, GMT and IST in plain English

GMT is associated with the historic time at Greenwich, London. UTC is a modern, highly precise international time standard. For ordinary clock conversion, GMT and UTC are often treated as the same zero-hour reference, but they are not the same technical system.

India uses IST, UTC+5:30 throughout the country. India does not currently change clocks seasonally. A meeting listed as 10:00 UTC is 3:30 PM IST.

Why Greenwich appears in time lessons

The international prime meridian at Greenwich became the zero-longitude reference used for global longitude. That historical decision is separate from India's 82.5°E standard meridian and from Ujjain's historical astronomical importance.

When the distinction matters

Use UTC for technical systems, aviation, computing and international coordination. Use GMT when a schedule or institution specifically uses that label. For a city meeting, use the named city and date because daylight-saving rules can change the local result.

Read about Greenwich, Ujjain and India's meridian · Convert IST to another city · See sources and calculation limits