How to calculate leap month? What are the rules?

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 even there are rare exceptions such as March and April of 1990. September, 10,1month and1February are big for four consecutive months.

The best way is to find the least common multiple of the number of days in the tropical year and the number of days in the lunar month: we hope that the number of days in m tropical years is equal to the number of days in n lunar months, that is, there should be an equation: m × 365.2422=n × 29.5306.

The origin of lunar calendar and solar calendar:

1, the lunar calendar in astronomy mainly refers to the calendar arranged according to the moon phase cycle, with the moon circling the earth once (with the sun as the reference, the actual moon runs for more than one week). ) is January, that is, the calendar based on the moon, with twelve calendar months in a year.

Lunar calendar is one of the traditional calendars in China, also known as "Han calendar" and "Old calendar". In the process of calendar development and evolution, the appearance of 24 solar terms was used to guide agricultural production scientifically, forming the lunar calendar. Although the lunar calendar and the lunar calendar are commonly known as the Han calendar and the old calendar, there is a difference between the lunar calendar and the lunar calendar (Han calendar). The traditional calendar in China is actually a kind of lunar calendar.

2. Gregorian calendar is a calendar based on the movement cycle of the earth around the sun. The Gregorian calendar year is approximately equal to the tropic year, one year 12 months. This "month" has nothing to do with the first lunar month.

The month and date of the solar calendar are very consistent with the position of the sun on the ecliptic. According to the date of the solar calendar, we can clearly see the changes of cold and warm seasons in a year. But every month, you can't see the new moon, the new moon, the new moon.

The Gregorian calendar prevailing in the modern world is a kind of solar calendar, with 365 days in a normal year and 366 days in a leap year, once every four years, once in a hundred years and once again in the 400th year, that is, there are 97 leap years every 400 years. The average length of the Gregorian calendar is only 26 seconds away from the tropic year, and it takes only one day to accumulate 3300 years.