What is Runyue? How did leap month come into being?

Lunar leap month runs once every three years, twice every five years, and 19 runs seven times.

The lunar leap month depends on the 24 solar terms in a year.

In the China lunar calendar, 24 solar terms are divided into 12 solar terms and 12 neutral terms. ?

The lunar calendar takes the moon as the cycle (lunar calendar), and the December calendar is 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. Deciding 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 autumnal equinox. If a lunar month has only solar terms but no neutral atmosphere, one more month will be added to the calendar as a leap month. Taking 2006 as an example, July of the lunar calendar happened to be a month with solar terms but no neutral atmosphere, so there was an adjustment error in July.

The date of the twenty-four solar terms of the lunar calendar is postponed month by month, so in some lunar months, the gas falls at the end of the month, and it will be out of gas next month.

Generally, there will be a month without gas every two years, which coincides with the year when leap months are needed. Therefore, the lunar calendar stipulates that non-neutral months are leap months.