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The Coordinated Universal Time ( English coordinated universal time , French Temps universel coordonné ), short UTC is valid botanical world time . It was introduced in 1972. If you add one hour to UTC, you get Central European Time (CET), which is temporarily valid in Germany, Austria, Switzerland and other Central European countries. The Central European Summer Time (CEST) valid in summer is obtained by adding two hours to UTC.

The current UTC is: 07:10

In contrast to universal time ( Universal Time UT), which follows the fluctuations of the earth's rotation continuously by the length of time unit is adjusted, the UTC follows these fluctuations by using leap seconds , while her every second that of evenly with SI-second continuous international atomic time ( TAI) is. The last leap second was inserted on December 31, 2016 with the second 23:59:60 UTC.

World map with time zones


UTC is the world time everywhere for times used where a globally uniform time scale is needed:

The times in the various time zones of the earth are derived from the coordinated world time, based on the prime meridian that runs through the London borough of Greenwich . UTC itself is used as the zone time for Western European Time (GMT / WET) - which is still called Greenwich Mean Time (GMT) in Great Britain, Ireland and West Africa .

Origin of the abbreviation

language acronym Text meaning
English CUT Coordinated Universal Time
French TUC Temps Universel Coordonné
Compromise UTC

unofficial English form:
"Universal Time Coordinated"

Before the abbreviation was standardized, the term Coordinated Universal Time, used in the English language, resulted in the abbreviation CUT, while the French variant Temps Universel Coordonné resulted in TUC. However, the International Telecommunication Union and the International Astronomical Union endeavored to establish a common abbreviation for all languages. In order not to prefer either of the two languages, the UTC compromise was chosen as the internationally uniform abbreviation, which is also alphabetically included in the other derivatives of Universal Time (such as UT1, UT2). The C is the basis of this determination for the coordinated switching seconds (engl. Coordinated, double. Coordonné ).


The UTC consists of the time and calendar date as a complete date . In the case of national or regional time zones, there is usually an indication of how many hours they deviate from UTC, for example UTC + 1 corresponds to Central European Time (CET) and UTC + 2 to Central European Summer Time (CEST) as well as Eastern European Time . The two time zones west and east of the date line , both of which have a time different from UTC by 12 hours, but in which the local date is different, are specified as UTC − 12 and UTC + 12 .

US President Obama at the National Counterterrorism Center in McLean, in the background the display of the Zulu period, 2015

This general time zone was designated by the letter Z , especially in aviation and NATO . Z stands for Zero (= zero). Therefore one speaks of Z-time or Zulu-time (according to the word Zulu assigned to the letter Z in the ICAO alphabet ). Z stands for zero meridian, ie prime meridian . However, this time specification is so rough that it can stand for both UT and UTC. In the meantime, however, the term Z-time is no longer used in aviation, but only referred to as UTC. In weather reports ( TAF / METAR ) and in US government agencies, however, you can still find the Zulu times ; the specification 1350Z means 13:50 UTC, see also ISO 8601 . GPS- relevant values, e.g. for the calibration of navigation devices, are marked with UTC, never with Z.

The standard time in Germany, Poland, Austria, Switzerland, and Italy is Central European Time (CET), which is equal to UTC plus one hour. The military also calls this Alfa time ( A ). During summer time, Central European Summer Time (CEST) applies , which corresponds to UTC plus two hours, designated in the NATO area with the code Bravo time (for B ).

An example from aviation should explain this: All times are specified internally as UTC time, e.g. B. UTC 13:52. Pilots who see this time look up in a directory which deviation applies to their whereabouts, e.g. B. LT (Local Time), so local time Berlin = UTC +1. You now calculate: z. B. 13:52 + 1:00 = 14:52 local time in Berlin. However, this only applies in winter, with summer time it would not have to add one, but two hours.

A time specification in the form 14:52 UTC+1:00means 14:52 local time (local zone time) for a time zone that is one hour ahead of UTC, e.g. B. CET. UTC at this point in time is 13:52.

If dates and times are combined, the date should be complete; the time can be given with reduced precision. The time indication 23:20:50o'clock 12. April 1985is shown as follows:

  • Basic format: 19850412T232050
  • Extended format: 1985-04-12T23:20:50

Unless it is clearly clear from the context which time zone is meant, it must always be added which offset to UTC the specified time has

  • Basic format: 19850412T232050+0100
  • Extended format: 1985-04-12T23:20:50+01:00

Only then can the time specified in the example be clearly identified as UTC 22:20:50.

Even if the time is specified in UTC, this must be indicated by adding the time zone (+00: 00 or UTC or Z).

Reference UTC - TAI

As a result of the slowing down of the earth's rotation, UTC is lagging behind International Atomic Time (TAI) . On January 1, 2017, the difference between UTC and TAI was −37 seconds. Adding more leap seconds to UTC will increase this difference.


The coordination of the UTC is the task of the International Bureau of Weights and Measures (BIPM). Its Consultative Committee for Time and Frequency (CCTF), which consists of members and observers from various time institutes, ensures the worldwide coordination of UTC.

Time institutes worldwide manage the UTC for national purposes, for example the Physikalisch-Technische Bundesanstalt (Germany), the Federal Office for Metrology and Surveying (Austria) and the Federal Institute for Metrology (Switzerland). Their representations are then z. B. UTC (PTB) for Germany, UTC (BEV) for Austria and UTC (CH) for Switzerland. The UTC can be called up via the time server via the Internet.

Web links

Wiktionary: UTC  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Rec.ITU-R TF.535-2 (PDF file; 5 kB)
  2. Universal Time. In: Oxford Dictionaries: British and World English. Oxford University Press, accessed November 4, 2015 .
  3. National Institute of Standards and Technology (NIST): Frequently asked questions (FAQ). In: Time and Frequency Division. US Commerce Department, accessed on July 27, 2010 (English): “ In 1970, the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU). The ITU felt it was best to designate a single abbreviation for use in all languages ​​in order to minimize confusion. For example, in English the abbreviation for coordinated universal time would be CUT, while in French the abbreviation for 'temps universel coordonné' would be TUC. To avoid appearing to favor any particular language, the abbreviation UTC was selected. "
  4. IAU resolutions adopted at the XVIth General Assembly, Grenoble, France, 1976. (PDF) 1976, pp. 27/28 , accessed on November 5, 2015 (English): "Commissions 4 (Ephemerides / Ephemerides) and 31 (Time / L'Heure) ... Resolution no. 3 by Commissions 4 and 31 ... recommend ... that the following notations be used in all languages ​​... UT0 (i) ... UT1 (i) ... UT2 (i) ... UTC ... UTC (i) "
  5. The same applies to the sometimes used, not entirely standardized, but possibly more legible modification 1350z with a lowercase Z.
  6. Not "Alpha"; the ICAO / NATO alphabet specifies the spelling “Alfa” in order to ensure uniform international pronunciation.
  7. ^ Acronyms and locations of the timing centers. (PDF) Retrieved April 14, 2011 .
  8. for example: ptbtime1.ptb.de, ptbtime2.ptb.de, ptbtime3.ptb.de