In the graph below you see the time zone difference between Greenwich Mean Time and Central European Time. Drag the bubble to adjust the time and to see the corresponding time in the other time zone.
Greenwich Mean Time is the time zone of the 0 meridian, located in London, United Kingdom, including cities like London, Lisbon and Dublin (in the winter). Central European Time is the time zone of most central European countries, and the Nordics, with places like Paris, Berlin, Stockholm, Amsterdam, Madrid, Rome, Zurich and Warsaw.
Usually it is preferable to schedule meetings in the morning for the person in GMT and after lunch for the person in CET.
GMT, or Greenwich Mean Time, is the zero when it comes to time zones – they are all counted from the zero meridian that runs through the village of Greenwich.
While both the UK and Portugal are officially on GMT you need to pay attention to whether they are actually observing it or are using their own. Britain in the summer for example use British Summer Time – which is different than GMT.
London, Lisbon, Dublin, Edinburgh
GMT does not observe DST as it is the zero hour time zone – it never changes.
CET is, as the name implies, the time zone for Central Europe. Important to note is that in summer Central European Time becomes CEST, which stands for Central European Summer Time. In practice, “Central” means “Western” as Central European Time includes everything from the Nordics to Spain. Note that Portugal and the UK are not on CET but instead observe GMT and that Eastern Europe (every country from Finland and South) observe Eastern European Time.
All countries in Western Europe, except Portugal and the UK, observe Central European Time. This includes Germany, Sweden, Italy, Spain, Croatia, Montenegro and Gibraltar to name a few.
The list is long but includes Berlin, Oslo, Madrid, Rome, Tirana, Amsterdam, Paris, Warsaw, Bern, Geneva and Copenhagen.
Daylight Saving Time is applied in Central Europe/Western Europe. CET in that case becomes CEST – Central European Summer Time and is one hour different. CEST is observed between the last Sunday of March and the last Sunday of October.