How did the calendar come from?

Calendar, also known as solar calendar and perpetual calendar.

The origin of the perpetual calendar can be traced back to the ancient Western Zhou Dynasty. One day, a woodcutter named Wannian went up the mountain to cut wood and had a rest, and found that the shadow on the ground had moved quietly. I had a brainwave for ten thousand years, and thought of calculating time by the length of the sun shadow. A "sundial instrument" was designed for this purpose after ten thousand years. However, in rainy days, the sundial instrument lost its utility again. Inspired by the rhythmic and regular dripping sound of spring water on the cliff, Wannian designed a five-story leaky pot, which was timed by leaking water. After a long induction, he found that the length of the weather will repeat every 360 days. As long as you understand the laws of the sun and the moon, you don't have to worry about the inaccuracy of solar terms. Wan Nian took a homemade sundial instrument and a leaky kettle to see the son of heaven Zuyi, saying that festivals were not allowed to have nothing to do with the gods. Zu Ti praised it so much that he devoted himself to the study of seasons for thousands of years. After dozens of winters and summers, the 10,000-year-old solar calendar was finally completed, and he became a white-haired old man because of fatigue. Deeply moved, Zu Ti named the solar calendar "perpetual calendar" and named it "Shouxing of the Sun and Moon", from which "perpetual calendar" came.