What is CET (Central European Time)?

CET is one of the most widely used time zones in the world, covering a band of Europe from Spain in the west to Poland in the east. It is simple on the surface, with one catch: for half the year, it is not actually CET at all.

What does CET stand for?

CET stands for Central European Time, and it sits at UTC+1 - one hour ahead of Coordinated Universal Time. It is the winter standard time for a large, continuous block of continental Europe. When it is 12:00 noon UTC, it is 1:00 PM in any city on CET.

Which countries use CET?

CET covers most of continental Europe. The list runs across the centre and west of the continent and includes major capitals in nearly every direction.

Notably, the UK, Ireland and Portugal are not on CET. They sit one hour behind, on GMT (or WET), which is a common source of confusion when scheduling a call between London and a neighbour just across the Channel.

What is the difference between CET and CEST?

CET is the winter time. CEST - Central European Summer Time - is the summer daylight saving time, set at UTC+2. The clocks move forward one hour in spring and back one hour in autumn, so the same city is CET for roughly five months and CEST for the other seven.

When does CET change to CEST?

The EU changes the clocks twice a year on fixed Sundays. Clocks spring forward to CEST on the last Sunday of March, and fall back to CET on the last Sunday of October.

The switch is a rule, not a convention

The iana time zone database, the dataset every mac, phone and server reads its offsets from applies one shared EU rule to Berlin, Paris, Madrid, Rome and Warsaw alike: summer time begins on the last Sunday in March and ends on the last Sunday in October, both at 01:00 UTC (IANA tz database, europe file, release 2026c, 8 July 2026). That rule gives effect to Directive 2000/84/EC. The database describes itself as “code and data that represent the history of local time for many representative locations worldwide”.

The 01:00 UTC part is the useful detail. Because the transition is pinned to a fixed instant rather than to local time, every CET country changes at the same moment, so the gaps between European cities never move. Only the gap to countries outside the rule, such as the US, changes twice a year.

Is CET the same as GMT?

No. CET is one hour ahead of GMT. In winter, noon GMT in London is 1:00 PM CET in Paris. In summer the gap is still one hour, because both sides move their clocks together, but the labels change to BST and CEST. If you find UTC and GMT confusing, our explainer on UTC vs GMT untangles the two.

What it means for scheduling

The practical lesson: a single label like "CET" can mean two different offsets depending on the month, and the country you assume is on CET might be on GMT instead. Rather than tracking which zone is which, it is safer to read each person's real local time. That is exactly what Atlas does - pin people on a map and see the live local hour for each, daylight saving and all. If you are looking for a tool, we compare the Mac menu bar time zone apps and the time zone meeting planners.