What do leap months and leap years mean?

Leap month is a concept in the lunar calendar, which refers to the13rd month inserted in a certain year, and is called "leap month". Because the length of the lunar calendar is different from the Gregorian calendar, the running time of the sun in a year is 365.2425 days, while the lunar calendar is 354-355 days. Therefore, it is necessary to add a "leap month" to keep the corresponding relationship between the lunar calendar and the seasons. Leap month is very important for many people, for example, farmers need to plant crops according to the lunar calendar to get a better harvest, and important festivals such as choosing wedding dates should also refer to the leap month in the lunar calendar.

Leap year is a concept in the Gregorian calendar. It refers to a year in which 29 days fall in February, which is called "leap year". Because the time for the earth to revolve around the sun is not 365 days, but 365.2422 days, in order to keep up with the solar calendar, the concept of leap year should be introduced. According to the Gregorian calendar, a leap year is a year in which the Gregorian calendar year is a multiple of 4, but for some years such as 100, 200, 300, etc. Only leap years can be divisible by 400.

The concepts and calculation methods of leap month and leap year are different in different cultures and regions. For example, in China, the months added in leap years are usually between early summer and early autumn, while in India, leap months are usually in spring. Similarly, in the Islamic lunar calendar, the length of a month is 29 or 30 days, and astronomers will observe the position of the moon to determine the time. There is no concept of leap year. In a word, leap month and leap year are important concepts used in different cultures to calculate time according to the trajectory of the sun and the moon. The calculation methods and specific practices vary with different regions and cultural backgrounds.