How to calculate the algorithm of lunar calendar?

The lunar year is 12 or 13 months, and the number of days in each month is 29 or 30 days, and the leap year is 13 months. The average lunar year in China is 353 or 354 days, and the leap year is 384 or 385 days, with an average of about 365.2422 days per year (that is, the earth goes around the sun once).

The lunar calendar basically takes 19 as a cycle, corresponding to the same time in the Gregorian calendar. For example, in the Gregorian calendar, May 27th, 2006, 5438+0, May 27th 1982 and May 27th 1963 are the fifth day of leap April.

The month of the leap month is inferred according to the laws of the lunar calendar, which is mainly determined according to the coincidence with the 24 solar terms of the lunar calendar. Since the winter solstice, odd numbers are solar terms and even numbers are neutral. If it is the turn of the month, only the solar terms are not neutral, that is the leap month last month. ? The number of leap months in the lunar calendar is 29 or 30 days, just like normal months.

Extended data

Lunar calendar is a traditional calendar in China, and it is also called lunar calendar, Chinese calendar, summer calendar, Han calendar and Chinese calendar. The lunar calendar is not a simple lunar calendar, but a combination of yin and yang. Take the change period of the moon phase as the length of the month, add the "24 solar terms" component of the trunk calendar, and refer to the length of the tropical year of the sun as the year. By setting leap months, the average calendar year can adapt to the tropic year. The lunar calendar is a calendar based on the lunar calendar (summer calendar) and integrating the solar calendar. So strictly speaking, the lunar calendar in China should not be called lunar calendar, but a combination of yin and yang.

The lunar calendar belongs to a kind of lunar calendar: its years are divided into flat years and leap years. An average year is twelve months; A leap year is thirteen months. A month is divided into a big month and a small month, with 30 days in the big month and 29 days in the small month, and its average calendar month is equal to the full moon. Which month is older and which month is younger in a year is determined by calculation.

The lunar calendar is a calendar that takes into account the relationship between the sun, the moon and the earth. The lunar calendar does not consider the movement of the earth around the sun, so the changes of the four seasons have no fixed time in the lunar calendar and cannot reflect the seasons. Unlike the fixed solar year of 365 days or 366 days, the solar year sometimes differs from the lunar year by one month. In order to coordinate the number of days between lunar year and solar year, the "leap method" is used to adjust the total number of days in lunar period to the total number of days in tropic year of solar calendar.

Reference: Baidu Encyclopedia-Lunar Calendar