What is the law of leap month?

The earth goes around the sun once, and the number of months in a year cannot be odd zero, so there are only 354 days in a year 12 months. Compared with the actual year, it is about 1 1 day, which adds up to three years and 33 days. So there must be a leap month every three years, and there are three or four days left, which adds up to two years. * * * The remaining 25 or 26 days.

Lunar calendar is a traditional calendar in China. The traditional lunar calendar is based on the lunar calendar and combined with the solar calendar, that is, the combined calendar of yin and yang. The solar calendar is based on the tropical year when the earth revolves around the sun.

The lunar calendar determines the date and month according to the change of the moon's profit and loss and the phase of the moon. The average lunar month is 29.5306 days, and 12 lunar month is 354 days or 355 days, which is about 1 1 day different from the tropical year of the solar calendar (about 365.25 days), and the accumulated time difference in three years will exceed one month. Because of the solar calendar, the lunar calendar is a calendar that takes into account the relationship between the sun, the moon and the earth, and belongs to the yin-yang calendar.

Because the pure lunar calendar does not consider the movement of the earth around the sun, the changes of the four seasons have no fixed time on the lunar calendar and cannot reflect the seasons. Unlike the fixed solar year of 365 days or 366 days, the solar year sometimes differs from the lunar year by one month. In order to coordinate the number of days between the lunar year and the solar year, the lunar calendar adopts the "leap method" to adapt to the total number of days in these two years.