After Li Shimin ascended the throne, Li Yin revised the Tang calendar and made further research and was reused. He was appointed as the general of Taishi Bureau. Taishi Museum was in charge of astronomy, calendar, landform and geography of the whole country at that time, which was consistent with Li's talent and specialty. Therefore, after Taishi Bureau, Li was like a duck to water, and his talents were fully displayed.
Because in ancient times, if you had different skills, it was generally believed that under the extremely underdeveloped social environment of ancient science, this was also an ominous sign that the world would change greatly. It is said that the House Classic was written by Li. The most important thing for ordinary people is the house, and good feng shui can make the house peaceful. Therefore, Li's theory actually treats the house as nature and pays attention to the unity of man and nature.
Yuan Tiangang is also good at this. After his death, he was buried behind a mountain in the suburb of Chang 'an County. However, Yuan Tiangang was intact, and Li was indeed stolen. According to legend, this is exactly what Li expected. The ancient calendar calculated the cycles of heavenly stems and earthly branches, but these cycles also became the burden of the calendar. Through Li's research, he resolutely abolished this calculation method, or Li is more powerful and courageous than Yuan Tiangang.
With continuous research and efforts, both of them have reached the height of mutual admiration, but in terms of calendar, Li is even better, and can calculate the astronomical phenomena so accurately.