What Is GMT?
Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, historically used as the world's reference time. Today it is also the name of the time zone used by the United Kingdom and some other countries in winter, which is equal to UTC+0.
GMT vs. UTC
For everyday purposes they show the same time, but UTC is the modern atomic-clock-based standard, while GMT is now mainly a time zone name.
Summer Time
The United Kingdom switches to British Summer Time (BST, UTC+1) in summer.
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🔗 Related Terms
More Time & Dates Terms
- 24-Hour Clock (Military Time)
- Business Days
- Calendar Quarter
- Chronological Age
- Day of the Year
- Equinox
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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.