According to what did the ancients in China make calendars?

Based on the bucket handle of the Big Dipper, the calendar has twelve dates (namely, Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai), which is the earliest ephemeris in China. In the emperor's time, the ancient ephemeris was revised. "Gaidi studied ephemeris and built five elements to get news, so he has the official of heaven and earth, which is called the five senses." This passage quoted from "Historical Records" Volume 26 "Almanac IV" means that the ephemeris before the emperor was not perfect. In the emperor's period, the emperor began to re-examine the original ephemeris, and established Jin Mu's five elements of fire, water and soil, plus twelve, ugliness, yin, Mao, Chen, Si, Wu, Wei, Shen and Tu. The five senses of gold, wood, water, fire and earth were established, and each of them performed its duties and formulated a new calendar. This is the combination of yin and yang. Xuanyuan in March is also called the Yellow Emperor's tortoise shell calendar (referred to as the imperial calendar).