The difference between CET or CEST and UTC (Coordinated Universal Time) is given by
CET = UTC + 1h,
CEST = UTC + 2h.
Daylight saving time (DST) was introduced in Germany by a decree of the Federal Government. The most recent related decree (Bundesgesetzblatt 2001 part 1, vol. 35, p. 1591, July 2001) states that beginning with 2002 and until further notice, daylight saving time shall be introduced between the last Sunday of March and the last Sunday of October.
In Germany, DST was established during wartime and more recently since 1980. All member states of the European Union follow the same schedule with respect to DST. World-wide several other schedules exist.
The Physikalisch-Technische Bundesanstalt PTB is entrusted by the Time Act to realise and disseminate legal time to the public. The most popular means is the transmission of standard frequency and time signals by the transmitter DCF77 (Working Group 4.42).
Sterne und Weltraum, Sonderheft Nr. 5 "Zeit - Das ewige Rätsel", Hüthig Verlag, Heidelberg, 2000
Zemanek, H., Kalender und Chronologie, Oldenbourg Verlag, München,Wien 1990 (vergriffen)
Lichtenberg, H., Gerhards, L., Graßl, A., Zemanek, H., Die Struktur des Gregorianischen Kalenders, Sterne und Weltraum 37 (1998), S. 326 - 332
Coyne, G. V., Hoskin, M. A., Pedersen, O. (Hrsg.), Gregorian Reform of the Calendar, Proceedings of the Vatican conference to commemorate its 400th anniversary 1582-1982, Vatikan-Stadt 1983
German standard definition DIN EN 28601, Beuth Verlag GmbH, Berlin, Germany, (1993)
"Feiertage im Ausland", distributed by: Germany Trade and Invest, Villemombler Str. 76, 53123 Bonn, www.gtai.de Bestellnr. 17301,