Why is leap month 29 days or 30 days?

The lunar year has 12 months. The number of days in a month depends on the period of the moon's orbit around the earth. Leap year is 29 or 30 days. The leap year is March. The average number of days in the China lunar calendar is 353 or 354. The leap year is 384 or 385 days. The calendar year (also known as the tropic year) has an average of 365.2422 days per year.

Monthly calendar is a kind of monthly calendar, and the number of days in each month is calculated according to the monthly profit and loss. A year's time is based on 12 months, that is, the tropic year, and it is increased by one month at regular intervals. This month is a month, so the lunar calendar is 13 months.

There is no title of 13 months in the lunar calendar. According to the rules of the calendar, leap month is released in the same month after any month. Repeated months are leap months. For example, the leap month after April is called leap month.

The month plus leap month, inferred from the laws of the lunar calendar, is mainly determined according to the 24 solar terms of the lunar calendar. From the winter solstice, when the odd number is a solar term, when the even number is a mid-term, if there is only a solar term at the beginning of the month without a mid-term, then last month is a leap month.

Extended data

There are three kinds of calendars in the world:

One is the solar calendar, in which the time for the earth to revolve around the sun is one year, and the number of months and days in a year can be specified artificially;

One is the lunar calendar, in which the time for the moon to circle the earth is one month, and only a few months in a year can be specified artificially;

The third is the lunar calendar, that is, the average time for the moon to make a circle around the earth is January, but by setting leap months, the average number of days in a year is equal to the average time for the earth to make a circle around the sun, such as the Han calendar and Tibetan calendar in China.

Therefore, China's Han calendar is not a lunar calendar, but a yin-yang calendar.

The lunar calendar and the solar calendar in the Han Calendar have their own uses. The lunar calendar can indicate the moon's profit and loss, and can also predict the tides.

The lunar calendar is more useful. Twenty-four solar terms are a great invention in ancient China. It shows the position of the earth in orbit and reflects the annual apparent movement of the sun, which is most suitable for guiding agricultural activities. Therefore, China's traditional calendar is a combination of yin and yang, which is called the lunar calendar. Therefore, the lunar calendar is different from the lunar calendar, and it is not appropriate to call the lunar calendar the lunar calendar.

The sun and the moon are calendars that people hang in the sky. Year after year, the earth revolves around the sun, and everything on the earth lives and breeds in the cycle of the sun and the moon.

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