Logo of the Physikalisch-Technische Bundesanstalt
Panoramic view of the clock hall at PTB with the four caesium clocks CS1, CS2, CSF1 and CSF2.

Realisation of Legal Time in Germany

The German Time Act of 1978 (Bundesgesetzblatt 1978, part I, p. 1110-1111), recently modified and broadened to a Law on Units and Time (BGBl. part I, p. 1185, July 11, 2008) lays down Central European Time CET or Central European summer Time CEST as legal time in Germany, which ought to be used in official and business affairs. The time law can be understood as a continuation of legal practice going back to 1893 when mean solar time at 15 degree eastern longitude was laid down as legal time for the German Reich. Before the date, numerous regulations existed for the use of local times throughout the country. The law of 1893 was enacted only a few years after a consensus had been reached on the estabilishment of a system of 24 time zones of 15° longitude widht with the reference meridian (°0) passing through Greenwich.

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).

Literature on German legal time

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

Regulations regarding calendar, date, and time in Germany:

German standard definition DIN EN 28601, Beuth Verlag GmbH, Berlin, Germany, (1993)