In 1979, the Shaanxi Astronomy Observatory (CSAO,now National Time Service Center) preliminarily established independent system of Local Atomic Time (AT(CSAO)) and Universal Time Coordinated (UTC(CSAO)) by using domestic hydrogen atomic clock and rubidium atomic clock.

In 1980, CSAO imported cesium atomic clock made in America to keep time and participated in International Atomic Time System.

In 1980, the National Institute of Metrology of participated in the International Atomic Time calculations.

In 1990, Chunghwa Telecom Laboratory in Taiwan participated in International Atomic Time calculations.

In 1995, the Beijing Institute of Radio Metrology and Measurement (203 China Aerospace Science & Industry Corp) joined in the International Atomic Time calculations. And then in 2004, Hong Kong Observatory joined in the calculations. Since 2003, the Macao Meteorological and Geophysical Bureau participated in the Integrated Atomic Time System of China.

To further enhance the accuracy and stability of atomic time of China, Joint Atomic Time of China (JATC) which joined in the International Atomic Time calculation was established by the Shaanxi Astronomy Observatory in conjunction with other institutions in 1985.

In the first stage, from 1985 to 2002, members of JATC were: Shaanxi Astronomy Observatory, Shanghai Astronomical Observatory, Beijing Astronomical Observatory, Wuhan Institute of Geodesy and Geophysics, and 203 China Aerospace Science & Industry Corp. From 2003 to 2006, the members of second stage includes: National Time Service Center, Shanghai Astronomical Observatory, Macao Meteorological and Geophysical Bureau, Xi'an Institute of Space Radio Technology, Rongcheng Station of "Changhe 2", Helong Station of "Changhe 2", Wuhan Institute of physics and Mathematics, WuHan University, Urumqi Observatory, etc.

TIPS: Atomic Time(AT) and Universal Time Coordinated(UTC)

Atomic Time and Local Atomic Time: (In 1967, the “second” was redefined from earth rotation to atomic physics, by the 13th International Metrology Congress, as exactly "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 Caesium-133 atom" (bipm.org); This standard time, determined by the frequency of atomic oscillation, is called atomic time. The atomic time scale produced and maintained by a set of atomic clocks in laboratory K is called local atomic time TA (k) of the laboratory.

Coordinated Universal Time: Coordinated Universal Time is a time scale maintained by the International Bureau of Weights (BIPM) and the International Earth Rotation Service Organization (IERS), which represents the combination of international atomic time TA and universal time UT1. Since 1972, it has become the official time of the world, and the basis of standard time and standard frequency signal transmission services.