CET (Central European Time)- which is used in most parts of the European Union, is a standard time which is 1 hour ahead of Coordinated Universal Time (UTC). The time offset from UTC can be written as +01:00. The same standard time, UTC+01:00, is also known as Middle European Time (MET, German: MEZ) and under other names like Romance Standard Time.
The 15th meridian east is the central axis for UTC+01:00 in the world system of time zones. As of 2011 all member states of the European Union observe summer time; those that use CET during the winter use Central European Summer Time (CEST), UTC+02:00, daylight saving time in summer.