GMT vs UTC: Are They the Same?
For everyday use GMT and UTC are the same time, but they are defined differently.
What each one is
GMT is a time zone, mean solar time at the Greenwich meridian, used in the UK in winter. UTC is Coordinated Universal Time, the global standard based on atomic clocks, with leap seconds added to keep it in step with the Earth's rotation.
Which should I use?
Use UTC in software, logs and scientific work because it never changes with the seasons. Use GMT for UK winter time, and UK time for the whole year.
Frequently asked questions
Is London always on GMT?
No. London uses GMT in winter and BST, which is UTC+1, in summer. UTC never changes.
Clock change guides
- What Is Daylight Saving Time (DST)? A Plain-English GuideWhat daylight saving time is, how it works in the UK, Europe and the US, why it exists, its history, who uses it and the argument over scrapping it.
- Why Do the Clocks Go Back in October? The Real ReasonThe clocks go back in autumn to return the UK to GMT, so winter mornings are lighter. The history, the rule, what time it happens and what changes for you.
- When Do the Clocks Go Forward Again After Going Back?When the UK clocks go forward again after the autumn change, how long the UK stays on GMT, when evenings get lighter and how to remember to reset your clocks.