National laboratory for time and frequency

Currently, Croatia has legal time defined by legislation, but there is no NMI or DI responsible for legal time keeping and dissemination.

Establishment of the National laboratory for time and frequency within the CALT project is coordinated and supported by the Croatian Metrology Institute with the mission to provide official Croatian time and related quantities to support a wide range of uses in industry, national infrastructure, research, and among the general public.

Time measurement is just as much a part of our daily lives today as it is a part of many fields of science and technology. This term is used for the measurement of the length of time intervals, for the recording of the frequency of events during a particular interval of time, and for the dating of events on a time scale. The dating of events and the coordination of various activities in a modern society are recognized as being so important that in many countries it is regulated by legislation how legal time is to be stated. Border-crossing traffic and communications require that the thus determined times of day of the countries are to be coordinated with one another.

Internationally agreed time scale defined through a second, one of seven base units of the International System of Units (SI), will be realized in the National laboratory for time and frequency. Current SI definition of second is “the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom”.

Establishment of the National laboratory for time and frequency in CALT is a comprehensible option, since the so called quantum or optical atomic clock will be developed in CALT, the successor of the rf clock which is the basic instrument in each national laboratory for time measurements.