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Leap second on December 31, 1995

31.10.1995

The Physikalisch-Technische Bundesanstalt (PTB) has been entrusted by the Time Act of 1978 to realize and distribute the legal time for the Federal Republic of Germany. For this purpose, the PTB developed four cesium atomic clocks whose time readings differ by less than one millionth second per year. It is on these atomic clocks that Germany's legal time is based today.

Our everyday life is, however, still guided by the mean solar time which is determined by the rotation of the earth. Leap seconds which are added as required - preferably in the middle or at the end of a year - ensure that the legal time does not differ from the nonuniform mean solar time by more than one second, in spite of the variations of the earth rotation.

The Central Bureau of the International Earth Rotation Service in Paris has now laid down that on December 31, 1995, a leap second - the thirtieth - should be intercalated in the Coordinated Universal Time Scale (UTC).

The PTB, too, will follow this international regulation and add a second to its Coordinated Universal Time Scale UTC(PTB). As the legal time of the Federal Repuplic of Germany - the Central European Time MEZ(D) - differs from the UTC(PTB) by one hour, the leap second will be intercalated at the end of the first hour of January 1, 1996. Thus the minute beginning on January 1, 1996, at 0:59:00 MEZ(D) will have 61 seconds.

Radio clocks receiving the time signals of the DCF77 time transmitter will automatically allow for the leap second; other clocks meant to remain in agreement with legal time must be stopped for a period of one second.