How is the leap month in leap year stipulated?

The jingle formula of leap month is as follows: leap in three years, leap in five years and leap in nineteen years.

First, the interpretation of the jingle formula of leap month

A cycle of nineteen years and seven months. Three years without leap, three years on both sides leap. There will be no leap month in two years, and this cycle will continue for another eight years. The last three years have not been a leap, and we look forward to the next year next week. This is a unique leap year calculation method in the lunar calendar. Set a leap month every three years, two leap months every five years and seven leap months every nineteen years. This cycle continues.

Second, the origin of leap month

Leap moon refers to a phenomenon in the lunar calendar. The lunar calendar arranges the big moon and the small moon according to the moon's full and short days, that is, the long and short days of the moon. This is the cycle of the moon's profit and loss. The big moon has 30 days and the small moon has 29 days, and a year is 12 months ***354 days. The month of the lunar calendar has no seasonal significance, so the difference between one year and the year of the solar calendar is only 17 years, and the date of the lunar calendar is upside down with the seasons.

Third, the calculation method of the ancients

The ancients did this to make the lunar calendar more practical. Therefore, they combined the solar calendar with the lunar calendar and creatively invented the twenty-four solar terms, that is, the time when the sun runs along the ecliptic is counted as one year. Then according to the law of the sun's movement, the ecliptic plane is divided into 24 nodes representing 24 solar terms. On the other hand, the lunar calendar counts the time for the moon to go around the earth as one month, and a year is 12 months.