Who calculated the perpetual calendar?

According to legend, a long time ago, there was a young man named Wannian. One day, he went up the mountain to cut wood, because the sun was too hot, so he sat in the shade and rested. Suddenly, the movement of the shadow on the ground inspired him. After returning home, he spent several days and nights designing sundials.

But in cloudy, rainy and foggy days, because there is no sun, the measurement will be affected. Later, the dripping spring on the cliff aroused his interest, and he began to make a five-story clepsydra. As time went on, he found that the length of the weather would repeat every 360 days.

At that time, the monarch was called Zu Ti, and the unexpected weather made him very upset. After hearing about it for ten thousand years, I couldn't help but take a sundial and a clepsydra to see the monarch and tell Zu Ti the truth about the movement of the sun and the moon. Zu Ti was very happy after hearing this, and felt very reasonable.

So I left for ten thousand years and built the Sun and Moon Pavilion in front of the Temple of Heaven, as well as the sundial platform and the Leaky Pot Pavilion. Zu Ti said to Wannian: I hope you can accurately measure the laws of the sun and the moon, calculate the exact time in the morning and evening, and create a calendar to benefit people all over the world.

Winter goes and spring comes, year after year. Later, after long-term observation and careful calculation, it took 10 thousand years to calculate the accurate solar calendar. When he showed his successor the solar calendar, he was covered with silver whiskers. The monarch was deeply moved. In order to commemorate the achievements of 10 thousand years, he named the solar calendar "perpetual calendar" and named it the birthday star of the sun, moon and moon.

Calendar principle

No matter what kind of calendar, there is a problem of coordinating the relationship between calendar day period and astronomical period. In principle, the calendar month should be equal to the new moon, and the calendar year should be equal to the Tropic of Cancer. However, because the first month of the lunar calendar and the return year are not complete days, calendar months must be divided into large months and small months, and calendar years must be divided into normal and leap years.

Through the proper collocation and arrangement of big month and small month, flat year and leap year, the average calendar month is equal to the new moon, or the average calendar year is equal to the tropic year. This is the main content of the calendar.