How many days a month are there in leap year?

Leap year1-65438+February is 3 1 day, 29 days, 3 1 day, 30 days, 3 1 day, 3 1 day, 30 days respectively.

Ordinary leap year: a year divisible by 4 but not by 100 is an ordinary leap year. (For example, 2004 is a leap year, 1999 is not).

Century leap year: the century leap year can be divisible by 400. (For example, 2000 is a leap year, 1900 is not).

The establishment of leap year is to make up for the time difference between the number of days in a year and the actual period of revolution of the earth caused by man-made calendar regulations. The year to make up for the time difference is leap year.

Where there is a leap day in the solar calendar (February 29); Leap surplus (leap surplus). The time difference between the lunar calendar and the tropic year); Please note that leap year (a term in the Gregorian calendar) is not directly related to leap month (a term in the lunar calendar). The Gregorian calendar has only leap years and peace years, with 365 days in a normal year and 366 days in a leap year (one more day in February). There may also be leap months in a normal year (for example, 20 17 is a normal year, and there are leap months and leap months in the lunar calendar).

For example, 20 16 and 2020 are leap years.

Extended data:

Leap years include years with leap days in the solar calendar or summer calendar, and years with leap months in the China lunar calendar.

1, leap year in Gregorian calendar

The period of the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365.438+09 days), which is the tropic of cancer. The Gregorian calendar has an average of only 365 days a year, which is about 0.2422 days shorter than the tropical year, and accumulates about one day every four years. Add this day to the end of February (that is, February 29), so the length of a year becomes 366 days, and this year is a leap year.

It should be noted that the Gregorian calendar was adapted from julian calendar in Rome. Because we didn't realize the problem of 0.0078 days in a year at that time, from 46 BC to16th century, a * * * accumulated 10 days in excess. Therefore, Pope Gregory XIII at that time set the artificial date of 65,438+0,582,65,438+0.05 as 65,438+0.00,65,438+0.05. And began to implement the new leap year regulations.

In other words, it is stipulated that the Gregorian calendar year is an integer hundred, the leap year must be a multiple of 400, and the average year is not a multiple of 400. For example, 1700, 1800 and 1900 are normal years, and 2000 is a leap year. Since then, the average annual length is 365.2425 days, with a deviation of about 4 years 1 day. According to a leap year every four years, there will be an average of 0.0078 days per year, which will be about 3 days after 400 years.

So every 400 years, three leap years will be reduced. The calculation of leap year comes down to what is commonly said: leap every four years; Do not leap in a hundred years, and leap again in 400 years.

Leap year from 1950 to 2050:

1952、 1956、 1960、 1964、 1968、 1972、 1976、 1980、 1984、 1988、 1992、 / kloc-0/996、2000、2004、2008、 20 12、20 16、2020、2024、2028、2032、2036、2040、2044、2048。

Because the rotation speed of the earth is gradually decreasing and the revolution speed is relatively more stable, the above system will also have small errors after a longer period. According to the calculation, there will be a day's error every 8000 years, so the British astronomer John Herschel suggested that 4000 AD should be the average year, and then to 12000, and 2000 should also be the average year.

But this proposal has never been formally adopted. The reason is that in 4000, the exact speed of the earth's rotation is still unpredictable, and we can make a judgment by referring to the real data at that time. Therefore, in the long run, the fine-tuning of leap years should not be determined by a predetermined system, but should be uncertain at any time.

2. Lunar leap year

As a kind of China lunar calendar, the number of days in each month depends on the monthly deficit, and the time of one year is based on 12 months, and the normal year is about 1 1 day less than a tropical year. In order to close the earth's orbit around the sun, that is, the tropic year, one month is added every two to four years, and the added month is a leap month.

The month of the leap month is inferred according to the laws of the lunar calendar, which is mainly determined according to the coincidence with the 24 solar terms of the lunar calendar. The year with leap month is 13 months, and the calendar year is 383 to 385 days. This year is also called leap year. For example, in the lunar calendar 1984, there are two October, which are usually called the first October and the last October (that is, leap month). The calculation of leap month in lunar leap year is one leap in three years, two leap in five years and seven leap in 19.

The lunar calendar basically takes 19 as a cycle, corresponding to the same time in the Gregorian calendar. For example, in the Gregorian calendar, May 27th, 2006, 5438+0, May 27th 1982 and May 27th 1963 are the fifth day of leap April.

References:

Baidu encyclopedia-leap year