How is the lunar calendar calculated?

The lunar calendar is a traditional calendar adopted in China, also known as the summer calendar, the Chinese calendar, the old calendar, folk also called the lunar calendar. It uses a strict lunar cycle to set the month, and sets the leap month to make the average length of the year similar to the regression year, both lunar month and solar year, so in essence it is a yin and yang calendar. In the lunar calendar, the first day of the month is the day when the sun and the moon coincide with the solstice (the yellow longitude of the sun and the moon are equal). The average length of the lunar month is about 29.53059 days, so some months are 30 days. Some months are 29 days long, and some months are small. The date of the beginning of the month, according to the position of the sun and the moon projected set, not mechanical arrangement. The lunar calendar takes twelve months as a year, ***354 or 355 days, a difference of eleven days from the year of return. This is harmonized by the placement of seven leap months every nineteen years. The arrangement of the leap months is determined by the twenty-four solar terms.

The lunar calendar uses the time when the moon is full or full once as a month, ****29 days and a half. For ease of counting, the big month is customized to be 30 days and the small month 29 days, with the big and small months roughly alternating throughout the 12 months of the year. There are about 365 days in a lunar year, and there is no difference between a flat year and a leap year.

The lunar calendar does not take into account the orbit of the earth around the sun, thus making the change of seasons in the lunar calendar will not have a fixed time, it can not reflect the seasons, which is a great disadvantage. In order to overcome this shortcoming, people later set a new calendar, which is the so-called lunar and solar calendar. The summer calendar (also known as the lunar calendar or the lunisolar calendar), which is still in use in China, is this kind of lunisolar calendar. It is the same as the lunisolar calendar, with the time of the moon's fullness and shortness as one month, that is, 30 days in the big month and 29 days in the small month, but it also adjusts the four seasons by adding intercalary months, so that the average number of days per year is close to the number of days of the whole year in the lunisolar calendar. In the lunar calendar, there is a leap month about every two or three years. ～