The spacetime metric in the framework of general relativity includes two types of time, namely proper time and coordinate time. The proper time can be realized by a high-precision atomic clock according to the definition of the second, and is carried by the observer for the time measurement of the local reference system. The local time maintained by the navigation satellite clock belongs to the category of proper time. The coordinate time is determined by the spacetime metric of the global coordinate system. The International Astronomical Union (IAU) officially recommended the use of general relativity as the theoretical basis for the spacetime reference system in 1991, introduced the Geocentric Coordinate Time (TCG), and defined the coordinate time in terms of SI second (Li in Relativistic time comparison theory and high-precision time synchronization technology. PLA Information Engineering University, Zhengzhou, 2004 [1]).