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.