Central European Time (CET), used in most parts of Europe and a few North African countries, is a standard time which is 1 hour ahead of Coordinated Universal Time (UTC). The time offset from UTC can be written as UTC+01:00. The same standard time, UTC+01:00, is also known as Middle European Time (MET, German: MEZ) and under other names like Berlin Time, Warsaw Time and Romance Standard Time (RST), Paris Time or Rome 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 during the winter use CET use Central European Summer Time (CEST) (or: UTC+02:00, daylight saving time) in summer (from last Sunday of March to last Sunday of October). A number of African countries use UTC+01:00 all year long, where it is called West Africa Time (WAT), although Algeria, Morocco, and Tunisia also use the term Central European Time.