The origin of leap month

The origin of leap month is as follows:

To understand the origin of leap month, we must first understand the China lunar calendar. Lunar calendar is a traditional calendar in China, and it has other names, such as Chinese calendar, summer calendar, Korean calendar and Chinese calendar. The lunar calendar is a kind of lunar calendar, which can not only reflect the changes of the moon phase, but also reflect the changes of the four seasons.

Lunar calendar is based on lunar calendar, and its "month" is based on the length of the first month of the lunar calendar, which is 29.5306 days. There are 30 days in the first lunar month and 29 days in the second lunar month, with an average of one year 12 months and ***354 days. It is about eleven days less than the familiar solar calendar.

Then, if there is no leap month, it will make the weather inconsistent with the duration. Due to the disorder of time sequence, it is difficult to guide agricultural production activities If this year's Spring Festival is spent in the severe winter, it will appear in the midsummer after seventeen years.

In order to make the calendar better guide agricultural production and correctly reflect the changes of the four seasons, the clever ancients came up with the method of setting leap. After accurate calculation, the average length of the lunar year is divided into time series by placing 7 leaps every 19 years and adding 24 solar terms, which is as close as possible to the tropic year.

How to set a leap:

The length of a tropical year is 365.2422 days, while the length of a lunar month is about 29.5306 days. In order to make the average degree of lunar year as close as possible to the tropic year, namely:

M×365.2422=n×29.5305(m stands for tropical years, n stands for the number of moons, and m and n are integers).

After calculation and selection, our ancestors adopted the method of seven leap years in nineteen years, that is, seven leap years and twelve normal years were set every nineteen years. Then:

19× 365.2422 = 6939.438+08 (days)

12×12+13× 7 = 235 (Shuowangyue)

235× 29.5306 = 6939.438+0 (days)

The difference in the total number of days between them is only 0.0892 days, which shows that the tropic year and lunar year can be well coordinated according to the method of 19 years, so that the New Year's Day (Spring Festival) of the lunar calendar is always kept in the late winter and early spring. The ancients called 235 new moons "leap weeks".

The leap month in the early Han dynasty was placed after September, which was called the last September. About a thousand years ago, with the gradual refinement of the calendar, the arrangement method of leap months was also properly stipulated, that is, the month without neutral gas was designated as leap month. Generally speaking, every two years or so (every 30 lunar months on average) there will be one month without gas, which coincides with the year when leap months are needed.

Refer to Baidu Encyclopedia-Leap Moon for the above information.