datetime – What is the difference between UTC and GMT? – Stack Overflow
Posted by jpluimers on 2026/11/03
[Wayback/Archive] datetime – What is the difference between UTC and GMT? – Stack Overflow
TL;DR: they used to be different but have been the same for a while now.
The difference is summarised in [Wayback/Archive] Hans Kruse on Twitter: “TIL; I should use OffsetDateTime in Java. An interesting discussion on UTC vs GMT and the historical differences was posted on Stackoverflow. – UTC has leap seconds – GMT had stretched seconds Nowadays they are the same.”
The historic difference however means that when handling past timestamps, you need to be aware that the differ between GMT and UTC.
Which means it is worth to read the whole Stack Overflow question with the most important answers: a trip down memory lane.
–jeroen
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