On this day, 46 years ago, December 3, 1979 (October 14, 1979 in the lunar calendar), World Coordinated Time replaced Greenwich Mean Time. The World Radio Administrative Conference held in Geneva in early December 1979 passed a resolution to replace "Greenwich Time" with "World Coordinated Time" as the international standard time in the field of radio communications. Greenwich Mean Time is the international standard time that has been known to people for many years. Why should we switch to World Coordinated Time? Simply put, it's because Greenwich Time is not accurate enough. Greenwich Time is a time scale based on the Earth's self-rotation. Due to the annual fluctuations of the Earth's spin axis, the time produces an error of nearly one second every year. Therefore, in order to adapt to the development of modern science and technology, there is an urgent need for a more accurate international standard time. World Coordinated Time is a kind of coordinated time that continuously corrects solar time based on the earth's fluctuations relative to the axis of rotation, rotation rate and polar shift effects. The Bureau of International Time makes adjustments twice a year and transmits standard time signals around the world through standard time stations, so that the one-second error caused by Greenwich Time can be adjusted. The use of world coordinated time in the radio field will play an important role in aviation, navigation, synchronous digital communications and aerospace navigation. The adoption of this new international standard time marks the rapid development of modern science and technology.