How to calculate the lunar calendar in China?

China's lunar calendar is based on the lunar calendar (summer calendar) and integrated with the solar calendar, absorbing the 24 solar terms of the solar calendar as a supplement, and adjusting it to the tropic year through the leap method.

The lunar calendar is a combination of yin and yang, which refers to 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 Gregorian calendar, which is fixed at 365 days or 366 days, the Gregorian calendar sometimes differs from the Gregorian calendar by one month.

In order to coordinate the number of days between the solar calendar year and the lunar calendar year, the lunar calendar was produced. The method is to add 24 solar terms and "19 7 leap year" to the calendar (that is, add 7 leap years to 19 lunar year). There is one more leap month in the leap year of the lunar calendar, so there are 383-385 days in a year, while the average year of the lunar calendar generally has 353-355 days. ) make the average number of days in a year consistent with the number of days in the Tropic of Cancer. Therefore, this calendar conforms to both the moon and the periodic movement of the earth around the sun.