Recently, the International Bureau of Weights and Measures (BIPM) completed the first-ever calibration and comparison verification of key Beidou parameters in China as part of its Global Navigation Satellite System (GNSS) time transfer standards. The Chinese Academy of Metrology precisely measured the technical parameters of the two BeiDou-3 signal frequencies—B1C and B2a—laying a solid foundation for global users to obtain “standard time” via BeiDou.

　　Standard time serves as a vital foundation for services such as positioning, navigation, and time distribution; the globally recognized standard time is Coordinated Universal Time (UTC). More than 80 time and frequency laboratories worldwide participate in the BIPM’s International Atomic Time collaboration. Primarily through GNSS time and frequency transfer technology, they conduct high-precision comparisons of more than 400 atomic clocks across these laboratories. UTC is derived through weighted averaging, frequency calibration, and leap second adjustments. Each month, the BIPM reports the deviations between each laboratory’s standard time and UTC. Countries adjust their local times accordingly, thereby achieving global time uniformity.

　　The accuracy of GNSS time transfer standards is key to ensuring global time consistency. During this calibration, the Chinese Academy of Metrology, relying on national time and frequency measurement standards and advanced measurement equipment, assembled a multidisciplinary team of young researchers who continuously overcame key technical challenges—such as the precise measurement of time delay, antenna phase center calibration, and uncertainty evaluation—to ensure accurate and reliable calibration results. Upon completion of the calibration, the BIPM will use this standard to gradually carry out G1-level calibrations of critical laboratory links, further promoting the application of BeiDou-3 in global time and frequency laboratories. Currently, BeiDou-3 has fully assumed its primary service responsibilities. As the calibration, monitoring, evaluation, and international mutual recognition systems for the BeiDou time distribution links continue to improve, BeiDou will further provide global users with more accurate and reliable time distribution services.