A leap month is a way to set a leap month in a calendar. In Asia (especially China), leap month refers to one month added every two to three years in the lunar calendar. In order to coordinate the contradiction between the tropic year and the lunar year and prevent the lunar year from being out of touch with the tropic year, that is, the four seasons, 1 leap is set every 2~3 years. In ancient times, there was a leap week, and there were seven leaps in nineteen years. By the time of Linde calendar in Tang Dynasty, the fixed leap week was abolished, and the leap was set in the month without season, so it was leap time.
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Set the origin of the jump
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.
The current method of setting leap in lunar calendar is "19 years and seven leap years", that is, every two to three years, a lunar month that is the same as the previous month is added, and the added month is called leap month. The rules of leap method are based on 24 solar terms related to the tropic year of solar calendar. A tropical year is divided into 24 solar terms. If the twenty-four solar terms are discharged from beginning of spring to Great Cold, then the odd number is called solar terms and the even number is called neutral gas. In the lunar calendar, twelve Chinese qi are used to represent twelve months of a year, and the average interval between Chinese qi and Chinese qi will be nearly one day longer than that of a lunar month. In the long run, there will always be a phenomenon of qi at the end of the month, so there will be no qi next month, only solar terms (that is, the next qi will be in early February of the lunar calendar). So this lunar month without neutrality is called the leap month of last month.
The mid-year month of the lunar calendar is based on the length of 29.5306 days in the first lunar month, so the big month is 30 days and the small month is 29 days. In order to ensure that the first day of each month (the first day) must be a new moon, the arrangement of large and small months is not fixed and needs to be determined through strict observation and calculation. Therefore, it is common for the lunar calendar to be big and small for two consecutive months, and there have even been rare exceptions, such as 1990 in March, April, September, 10, winter and twelfth month.