The National Institute of Metrology of China has developed a strontium atomic optical lattice clock, NIM-Sr1, which has now been approved to participate in the calibration of international standard time. This marks China's inaugural breakthrough in this domain, representing a significant milestone in the nation's optical clock research endeavors. The accomplishment is poised to inspire greater participation from optical clocks worldwide, thereby amplifying China's influence within the international time and frequency research community.

At present, cesium atomic clocks boast an accuracy that ensures no more than one second of error over several hundred million years. In stark contrast, the latest optical clocks have elevated precision to new heights, achieving an accuracy that guarantees no more than one second of error over tens to hundreds of billions of years. Consequently, these optical clocks emerge as prime contenders to supplant cesium atomic clocks, redefine the 'second,' and calibrate international standard time with unparalleled precision.