Eight years of Zuo Zhuan recorded that there was no ice in February. Historians recorded this rare phenomenon in history. Obviously, this February refers to February in the weekly calendar, which is December in the summer calendar. If it is February in the summer calendar, it is already "the east wind thaws", and there is no need to make a big book. Another example is "Seven Years of Zhuang Gong", which says that "autumn is full of floods and there are no wheat seedlings". This also refers to the weekly calendar. Autumn in the weekly calendar is equivalent to May and June in the summer calendar, and the late-harvested wheat and "five-stubble seedlings" may be "washed away" by the flood. If the summer calendar is autumn, it's incomprehensible. For the same reason, the autumn sun in Mencius Teng Wengong refers to the hot weather in May and June in the summer calendar. For the same historical fact, the time and month recorded in Chunqiu and Zuozhuan are often different, and the time recorded in Zuozhuan is also different. Seclusion in Six Years in the Spring and Autumn Period says that "people in the winter and Song Dynasties took kudzu vine", while Zuozhuan says that "people in the winter and Song Dynasties took kudzu vine"; The father of Spring and Autumn Annals said that the king of Jin was killed in the spring. Zuo Zhuan recorded that the same thing happened in December of the fourth year, which shows that the historical materials based on Zuo Zhuan are useful in the summer calendar.
During the Warring States, Qin and Han Dynasties, there was a so-called "three orthodoxy", which believed that Xia Yin, Yin Chou and Zhou were the people who changed orthodoxy in turn in Xia, Shang and Zhou Dynasties, because "the monarch should be the new moon" and "easy to follow the color" to show that he was ordered by heaven. After Qin Shihuang unified China, the first year of the year was to build the Moon (that is, October in the summer calendar), but Xia Zheng was more suitable for the farming season, so October was not called the first month (the Qin Dynasty called the first month "the end of the moon"), and April was not corrected, so the collocation of spring, summer, autumn and winter was still the same as that of Xia Zheng. The early Han dynasty followed the Qin system. Biography of Wei Anhou in Historical Records records that Emperor Yuan Guang of the Han Dynasty killed in October and December in the fifth year (BC 130), and then said, "In the spring, Wu 'an was ill." Sima Qian did not say "next spring", but its spring, because October is the beginning of a year, and the spring of that year is after December of that year.
In the seventh year of Emperor Wu of the Han Dynasty (BC 104), taichu calendar began to be used, starting from the first month of the summer calendar. In the next two thousand years or so, except for Wang Mang and Wei Mingdi who once switched to Andrew, Wu Zetian and Tang Suzong who once switched to Zhou Zheng, Xia Zheng was widely used.