On this day 50 years ago, on October 31, 1975 (September 27, 1975 lunar calendar), Li Tianci successfully created the "Age of Ganzhi and Branches in the AD". In October 1975, Li Tianci, a young researcher at the Zijinshan Observatory of the Chinese Academy of Sciences, successfully created the "Age of Ganzhi and Branches in the AD", which provided a new auxiliary tool for the study of the history of science in our country. Ganzhi and branching days are an important content in our country's calendar. In ancient times, it was used to represent the year, month, day, cycle and cycle. Our country has used the age of Ganzhi for thousands of years without interruption or disorder, making it the oldest calendar method in the world. Ganzhi is still used in the lunar calendar. Converting the date of the Gregorian calendar is a rather troublesome problem when sorting out the rich scientific historical materials in our country. Sometimes, there are often dozens of branches on a page, and they all have to read the reference book one by one; some need to be calculated after finding out, which is time-consuming and prone to errors. Over the years, many people have tried to find a simple way to solve this problem, but they have not been successful. On the basis of summarizing the research results of predecessors, Li Tianci broke the superstition, liberated the mind, broke through the traditional old method, and researched and created the "Quick Check Plate for the Chronicle of Dry Branches in the AD". This kind of quick check plate is fast and accurate, and the estimated historical age is longer than the existing reference books. This kind of quick check plate is made of three layers of cardboard (or metal or plastic). Just rotate the time you want to check to a specific location, and you can immediately find out the Gregorian calendar date corresponding to a certain branch. For example, the "Earthquake" section of the "History of the Ming Dynasty ¡¤ Five Elements" records a famous earthquake in the history of our country: "In December of the 34th year of Jiajing, there was an earthquake in Shanxi, Shaanxi and Henan at the same time." In December of the 34th year of Jiajing, Ren Yin was in what year, month and day, and with a quick check plate, you will immediately know that it was January 23, 1556. The successful research of this kind of quick check plate provides a convenient and accurate auxiliary tool for the study of scientific historical materials such as ancient calendar, hydrology, meteorology, archaeology, phenology, and earthquakes in our country, especially for sorting out the records of celestial phenomena such as solar eclipses, lunar eclipses, meteors, comets, and novae in our country's ancient astronomical heritage. When Li Tianci was studying in middle school, he was interested in astronomy and calendars. In 1963, he initially created the "Quick Check Plate for the Chronicles of the Dry Branches of the AD", and at the same time developed the "Mutual Check Plate for the Hijri Calendar of the AD", "Quick Check Table for the Chronicles of Chinese History", "Quick Check Table for the Julian Day", and "Comparison Table for the Two Hundred-Year Lunar Calendar His research work attracted the attention of relevant units, and he was recommended to specialize in astronomy in the Department of Astronomy of Nanjing University. After Li Tianci arrived at Nanjing University, he studied Marxism and ancient astronomy, ancient Chinese, and Chinese history seriously, laying a solid foundation for his subsequent research work. Since the Cultural Revolution, he has further improved his consciousness, studied his business hard for the revolution, and spent many holidays in the library. During this period, he further studied and improved the "Accumulated Days Quick Check Table", and according to the needs of the masses, designed the "Accumulated Days Quick Check Table", which has wide practical value in industrial and agricultural production, transportation, etc.