How is the lunar calendar calculated?

Lunar calendar is a traditional calendar adopted by China, also known as summer calendar, middle calendar and old calendar. Some people call it the lunar calendar. It uses the strict lunar cycle to determine the month, and sets the leap month to make the average length of a year close to the tropic year, which has the attributes of lunar month and solar year, so it is essentially a kind of yin-yang calendar. In the lunar calendar, the date when the sun and the moon meet (the ecliptic is equal) is the first day of the month, that is, the first day. The average length of the first month of the lunar calendar is about 29.53059 days, so some months are 30th. Call the moon big; Some months are the 29th, called abortion. The date of the beginning of the month is calculated according to the position of the sun and the moon, not mechanically arranged. The lunar calendar takes1February as a year, ***354 or 355 days, which is different from the tropic year 1 1 day. Therefore, coordination is achieved by inserting 7 leap months every 19 years. The arrangement of leap month is determined by the 24 solar terms.

Legend has it that China's calendar originated in the Xia Dynasty.

Very scientific and practical, so it has been passed down to this day. The lunar calendar is divided into four seasons, twenty-four solar terms and annual festivals according to the natural days of the whole year.

The twenty-four solar terms of the lunar calendar include: beginning of spring, rain, fright, vernal equinox, Qingming and Grain Rain; Long summer, xiaoman, mangzhong, summer solstice, summer heat, summer heat; Beginning of autumn, first ripe, white dew, autumnal equinox, cold dew, early autumn frost; Beginning of winter, light snow, heavy snow, winter solstice, slight cold, cold winter.

In addition, the months in the whole year are set according to the cycle of the moon phase change. That is, the big month is 30 days and the small month is 29 days. The first day of each month in the lunar calendar is called "New Moon" and the fifteenth day of each month is called "Hope". On the "new moon" day, the moon runs between the sun and the earth, with its shadow facing the earth, but it appears at the same time as the sun, so people can't see the moon. On lookout day, the earth moves between the sun and the moon. The sun sets in the west and the moon rises in the east, so we can see the full moon.

Because the lunar year is about 355 days, which is about 1 1 day different from the earth year, there should be a leap month every 3 years and 7 leap months every 19 years. A year with a leap month is also called a leap year. The specific leap month depends on the elasticity of solar terms.

The lunar calendar is not only designated according to the time spent in the year of the return of the earth, but also according to the changes of the moon phases, and it is more practical with reference to the surrounding meteorological and phenological conditions and agricultural activities, so it has become a calendar with four distinct seasons and easy memory. In China, the lunar calendar is especially suitable for the vast areas of the Central Plains.