In the history of China, the use of Jiazi (trunk and branches) for chronology began in the Han Dynasty. Before the Qin and Han Dynasties and the early Han Dynasty, people used the Sui and Xing Dynasties. When Emperor Wu of the Han Dynasty changed the calendar and implemented the taichu calendar, he still used the traditional calendar. Therefore, there is "the first year of the beginning, the year number is not mentioned." Jiazi has been used for chronology since Emperor Wu of the Han Dynasty, but there was confusion in the transformation between Sui and Jiazi during this period. Some added a super-old, some added more super-old, and some didn't, such as directly using the year. However, during this period, some people marked Jiazi Year of the first year of the Tai Chu as Bingzi, while others marked Ding Chou. It was not until February of the second year of Emperor Han Yuan that the emperor promulgated a new calendar and fixed it with the seasonal calendar. The first year, the year number Ding Chou, the first year of Han Xing, the year number B. So the Jiazi (trunk and branch) chronology method was officially used, and the old star chronology was abolished. However, the official year of adopting Jiazi (trunk and branches) is Yiyou, so the first Jiazi year it encountered was Jiazi of Hanandi Yan Guang (Gregorian calendar 124).
At the end of the Qing Dynasty, some revolutionaries put forward the concept of the calendar year of the Yellow Emperor, and then deduced several starting points of the calendar year of the Yellow Emperor, one of which was 2697 BC, which happened to be the year of Jiazi. Therefore, there is a close relationship between the first year of Jiazi and the calendar of the Yellow Emperor. In recent years, many new suggestions have been put forward. * * * lists nine schemes about the calendar year of the Yellow Emperor. Among them, the first year of the Yellow Emperor happened to be the year of Jiazi in the lunar calendar: the plan in 2697 BC and the plan in 1997 BC. This plan is actually quite consistent with Jiazi's chronology, but it is also controversial, especially when the real age of the Yellow Emperor is being excavated. Once excavated, it is very different from this era, which is not conducive to use.