The first method is the method of AD chronology, which is the most commonly used method to calculate time. It originated in the ancient west. Because of its simple method of calculating time, it has been handed down by later generations and is still in use today. In order to calculate time, he simply divided it into BC and AD. Our present and future years belong to after A.D. If you see a long year in the history books, you should add BC.
The second is the calculation method of a certain year. In ancient China, the emperor was sacred to ordinary people. Generally, historians will announce the year number of the emperor. For example, the first year of King Jing refers to the first year of King Jing's administration. The first few years of the emperor's reign were years. For example, the second year of King Jing's reign is called the second year of King Jin. If you change the emperor, you change the year number. However, there are some special cases, such as Judy in the Ming Dynasty, who did not recognize the dominant position of the former emperor, so his title is more complicated.
The third is the moon algorithm. Lunar algorithm is also a commonly used time algorithm. It divides time according to the moon's waning and waning. This algorithm can not only calculate time, but also be helpful to agricultural production and life. For example, when the awning season comes, it means that this time is a good time for awning. China is a big agricultural country, and this algorithm is simple and practical for farmers. So it is very popular with farmers.