The origin of leap month? Is there a saying of leap moon in ancient times?

With the leap month, people can use the same calendar as the Tropic of Cancer.

So, what is the origin of leap month? Let's find out through the calendar.

China's lunar calendar is a combination of Yin and Yang, and leap month refers to adding months and dates to the calendar, so that the average length of the calendar year is close to the tropic year. The lunar calendar arranges the big moon and the small moon according to the full moon. The length of a moon is 29.5306 days, which is the cycle of the moon's profit and loss. The lunar calendar stipulates that the big month is 30 days, the small month is 29 days, and a year is 12 months. These twelve lunar months constitute the Han calendar year, with a length of 29.5306× 12 = 354.3672 days, which is less than the tropical year's 365.2422 days 10.88 days (that is, near 1 1 day), and each month is 0.9 1 day.

In this way, if after 17, the date of the lunar calendar will be reversed in the same season. For example, a year's New Year is spent in the snow. After 17, fans will be shaken to celebrate the New Year. Using such a calendar naturally cannot meet the needs of agricultural production. Therefore, since the Qin and Han Dynasties, the lunar calendar in China has been in parallel with the twenty-four solar terms, and the twenty-four solar terms have been used to guide agricultural production.

But if the lunar year consists of thirteen moons, the length is 29.5306× 13 = 383.8978 days, which is 18 days more than the tropic year. If the calendar is made according to the above regulations, there will be a strange phenomenon that the weather is inconsistent with the calendar and the time sequence is disordered and reversed. This is the contradiction.

Therefore, in order to overcome this shortcoming, our ancestors found the method of "leap moon" on the basis of astronomical observation, ensuring that the first month to March is spring, April to June is summer, July to September is autumn, and October to December is winter, and at the same time ensuring that the first year of the lunar calendar is in late winter and early spring (all above refer to the lunar season).

So what do you think of the lunar leap month? It depends on the 24 solar terms in a year.

The lunar calendar takes the moon as the cycle (lunar calendar), and the December calendar has a total of about 354 days; Combined with the almanac (solar calendar), the almanac is compiled according to the four-season cycle formed by the revolution of the earth. The monthly calendar is shorter than the annual calendar by 1 1 day. Therefore, it is necessary to add 7 leap months every 19 years to make up for the error.

Which month is a leap month depends on 24 solar terms. Lunar months usually include a solar term and a neutral atmosphere, such as the vernal equinox. If a lunar month has only solar terms and no neutral atmosphere, the calendar will regard that month as a leap month of last month. Take 2006 as an example. After July of the lunar calendar, there happens to be a month with only solar terms and no neutral atmosphere, so we set leap July to adjust the error.

The date of the twenty-four solar terms in the lunar calendar is postponed month by month, so in some lunar months, the qi falls at the end of the month and there will be no qi in the next month. Generally speaking, there is no gas for one month every two years, which is consistent with the year when leap months are needed. Therefore, the lunar calendar stipulates that non-neutral months are leap months.

Conclusion: The lunar calendar has a long history of setting up a leap month. The method of setting up a leap month can make the average length of the lunar year close to the tropic year, and the moon in the lunar calendar has distinct moon phase characteristics, maintaining the best characteristics of both the Gregorian calendar and the lunar calendar.