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What are a flat year and a leap year?

A normal year refers to a year in which there is no leap day in the solar calendar and no leap month in the lunar calendar. A leap year is a year divisible by 4 in a.d., but the whole hundred years (both digits are 0) must be divisible by 400 (for example, 1900 is not a leap year), and the rest are normal years.

For example, 1997 is a normal year, and 2002 is a normal year; 1996 is a leap year, and 2000 is a leap year. February in a normal year has 28 days, while February in a leap year has 29 days.

The leap year in the solar calendar has 366 days and February 29 days; The normal year of Gregorian calendar has 365 days, February 28th.

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.

Extended data

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); 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).

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.

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