Central European Time (CET) is the time zone of most European countries, specifically Albania, Andorra, Austria, Belgium, Bosnia and Herzegovina, Croatia, Czechia, Denmark (except Greenland and Faroe Islands), France (except overseas regions), Germany, Gibraltar, Hungary, Italy, Kosovo, Liechtenstein, Luxembourg, Macedonia, Malta, Monaco, Montenegro, Netherlands (except Caribbean island territories), Norway, Poland, San Marino, Serbia, Slovakia, Slovenia, Spain (except Canary Islands), Sweden, Switzerland and Vatican City.
CET alternates between UTC+1 (standard time) and UTC+2 (when daylight saving time (DST) is observed). All countries in the CET time zone observe DST (UTC+2) from 02:00 am on the last Sunday of March until 03:00 am on the last Sunday of October.
Warning: Many sources define CET as a constant UTC+1. In common usage however, CET usually refers to the time observed in most of Europe, be it standard time or daylight saving time.
Since there is some confusion around the definition of CET, we recommend quoting time in UTC offsets (e.g. 03:00pm UTC+2), or by referring to a specific time and location (e.g. "at 3pm on 31 July in Paris"). Ideally provide a link to a page on Time.is that will automatically convert the time to the user's own time zone, like this: https://time.is/3pm_31_May_2017_in_Brussels
See also: Central European Summer Time (CEST)