Why are there 400 leap years for every 97 years

The Gregorian leap year is defined as follows: the earth revolves around the sun.

A week is called a return year, and a return year is 365 days 5:48:46 seconds. Therefore, the Gregorian calendar stipulates that there are common years and leap years, and there are 365 days in a common year, which is shorter than the return year, and there are four short days in four years, so one day is added every four years, and there are 366 days in this year, which is a leap year. However, an additional day in four years is more than four return years, and there will be many days after 400 years, so there are three fewer leap years in 400 years, that is, only 97 leap years in 400 years, so that the average length of the Gregorian calendar year is similar to that of the return year.

Therefore, it is stipulated that if the year is an integer hundred, it must be a multiple of 400 to be a leap year, for example, 1900 and 2100 are not leap years.

Since the Earth's orbit around the Sun is 365 days, 5 hours, 48 minutes and 46 seconds, which is a return year, the Gregorian calendar defines a year as 365 days. The remaining time is about one day over four years, added to February, so that in a normal year there are 365 days per year, 28 days in February, 366 days in leap years, and 29 days in February. Thus, there are 97 leap years in every 400 years, with leap years having an additional day at the end of February, and 366 days in leap years.

How to calculate leap years: The number of years in the Common Era is divisible by four, that is, leap years; And there will be an error in this way, every 400 years there will be one less leap day, so it is stipulated that every hundred years (1900, 2000, 2100, 3000 cannot be divisible by 400 as common years; A leap year is divisible by 400. For example, 2000 is a leap year, and 1900 is not, the same.

There is usually a leap year every four years; Every four years there is a leap year and three common years.

A leap year was established to compensate for the difference between the number of days of the year and the actual orbital cycle of the earth caused by the man-made calendar. The year in which the time difference is made up is a leap year. There are 366 days in a leap year (31, 29, 31, 30, 31, 30, 30, 30, 31, 31, 31, 31, 30, 30, 30, 31, 31 and 31 in January and December).

Where there is a leap day (February 29) in the solar calendar, the leap more (the year is more than the leap year. The difference in time between the lunar calendar and the return year).

Causes. The usual explanation is to say how many days, hours, and minutes there are in a year, and after rounding up 365 days, there is still an excess, and after the accumulation reaches one day (24 hours), one more day is added, and the year in which one more day is added is a leap year. This explanation just tells you how to calculate, it is something that is set artificially.

The most fundamental reason is that the Earth's orbit around the Sun is 365 days, 5 hours, 48 minutes and 46 seconds (conjunction), which is a tropical year. The common year of the Gregorian calendar is only 365 days, which is about one day shorter than the return year, and the remaining time is about one day accumulated every four years, so one day is added at the end of February of the fourth year to make the length of the year 366 days, and this year is a leap year.

There are 97 leap years in the current Gregorian calendar every 400 years.

If a leap year is calculated every four years, an average of more days are counted per year, so that after 400 years, about three more days will be calculated. Therefore, every 400 years there is a reduction of 3 leap years. So the Gregorian calendar prescribes:

When the year is an integer hundred, it must be a multiple of 400 to be a leap year; A century year that is not a multiple of 400, and even a multiple of 4 is not a leap year.

4 years, but when the Gregorian year is a multiple of 100, it must be divisible by 400 to be a leap year. As 1900 was not, and 200 years were.

There is usually a leap year every 4 years.

A leap year is derived from the return period of the direct point of the sun, which is 365 days 5:48:46, which is called the return year, which is converted into days. For the sake of convenience, 365 is regarded as a year, which is the "common year".

The return year is 5:48:46 more than the usual year, and the cumulative 4 years are about equal to one day, so every 4 years there is a leap day, and this day is placed in February, becoming 29 days, and there are 365 days in that year, which is called "leap year", which is what we often call the Gregorian calendar.

However, if you calculate it precisely, the accumulated time in four years will be 44 minutes and 56 seconds more after a leap day in four years, and after four hundred years, the calendar year will be three days longer than the return year, so there should be three fewer leaps in the return year.

Therefore, it is a leap year that stipulates that the number of years in the Common Era is divisible by 4, and for the first year of each century, although divisible by 4, but not divisible by 400, it is still not a leap year. In this way, in 400 years, there were 100 leaps, but the number of leaps decreased by 3, resulting in 97 leap years. This is the starting bridge.

How to determine leap years:

1. There are 366 days in the boudoir year.

2. Every four years, there is a leap year, and the remaining three years are common years.

3. The number of years in the Common Era can be divisible by 4 as the boudoir year, but the number of years of the whole hundred (the single digit and the tenth digit are 0) must be divisible by 400 to be the boudoir year. Everything else is an ordinary year. For example:

The year 1900 is not a leap year because 1900 is a multiple of 100 but not a multiple of 400, whereas 2000 is a leap year because 2000 is a multiple of 400.

4. 29 days in February in boudoir years and 28 days in February in normal years.

The boudoir is a crystallization of the wisdom of our ancients, and the boudoir can deal with the problem of the year and the rotation of the earth well, so that the summer will not become cold and the winter will become hot.

In general, there is a leap year every 4 years. However, when encountering an integer multiple of 100 years, the missing family needs to be divisible by 400 to be a leap year, so it is possible to have a leap year 8 years apart. Leap years are established to compensate for the time difference between the number of days of the year and the actual orbital cycle of the earth caused by the artificial calendar.

There is no direct correlation between leap year (noun in the Gregorian calendar) and leap month (noun in the lunar calendar), which is only divided into leap years and peaceful years, with 365 days in a common year and 366 days in a leap year (one more day in February); There may also be leap months in a normal year (e.g. 2017 is a common year, and the lunar calendar has a leap month and a leap month in June).

The meaning of 400 years and leap is a multiple of 400 but also a leap year.

Usually, there are three common years and one leap year every four years. Gregorian calendar years are multiples of 4 and are generally leap years.

According to a leap year every four years, an average of more days are counted per year, so that after 400 years there will be about 3 more days, so that every 400 years there is a decrease of three leap years. Therefore, it is stipulated that the Gregorian calendar year is an integer hundred, and a leap year that must be a multiple of 400 is a leap year, and a multiple of 400 is a common year.

Original sentence: There is a leap in four years, no leap in a hundred years, and then an intercalary in four hundred years.

How to determine leap years:

Leap years are divisible by 400, or divisible by 4 but not by 100, and the rest of the years are common years. A leap year is divisible by 400, e.g. 2000 is a leap year of the century. Cons: Search.

Difference Between Leap Year and Peaceful Year:

1. The calculation method is different.

When the age is briefly divisible by 400 for a whole hundred years, it is a leap year, otherwise it is a common year; In the case of a non-whole hundred years, as long as it is divisible by 4, it is a leap year, and it cannot be divisible by 4 as a common year.

2. The meaning is different.

Leap years are created to compensate for the time difference between the number of days of the year and the actual orbital cycle of the earth caused by the man-made calendar. A common year refers to a year in which there are no leap days in the solar calendar or no leap month in the lunar calendar, and the harvest is usually the year.

3. The number of days is different.

There are 29 days in February in leap years, and there are 366 days in the year, leap years are divided into ordinary leap years and century leap years, ordinary leap years refer to the Gregorian calendar year is a multiple of 4, and not a multiple of 100, and a century leap year must be a multiple of 400. In a normal year, there are 28 days in February, and there are 365 days in the year. <>

There is not necessarily a leap year in 4 consecutive years. If the Gregorian calendar year is divided by 4 without a remainder, it is generally a leap year, and if it is a year of a full hundred years, it is a leap year if it is divided by 400 and there is no remainder, for example, 2100 divided by 400 has a remainder, so it is not a leap year.

Leap years are established to compensate for the time difference between the number of days of the year and the actual orbital cycle of the earth due to the artificial calendar of hail.

The year that makes up the time difference is a leap year, with a total of 366 days, one day more than a normal year, and leap years are also divided into ordinary leap years and century leap years.

Leap years are not directly related to leap months in the lunar calendar, and there may also be leap months in ordinary years, such as 2017 is a common year, and the source of the lunar calendar has a leap month in June.

Why is it "a leap in four years, no leap in a hundred years, and a leap in four hundred years".

We know that a year is the time it takes for the Earth to revolve around the Sun, and the actual time for the Earth to orbit the Sun is 365 days, 5 hours, 48 minutes and 46 seconds. For convenience, the letter liquid in ordinary years is calculated as 365 days, so that every four years it is less than 5 hours, 48 minutes and 46 seconds 4 = 23 hours, 15 minutes and 4 seconds, which is close to one day. Therefore, an additional day is added in February of the fourth year, which is called the Buried Leap Year (366 days).

Because, every four years or more is generally placed in the year when the number of years in the Common Era is divisible by 4, so, like 1988, 1992 、......It's all leap years. This is the principle of "every leap in four years".

Since a day is the time it takes for the earth to rotate one week, and a day is actually 24 hours, 24 hours - 23 hours 15 minutes and 4 seconds = 44 minutes and 56 seconds, so that every four years an extra 44 minutes and 56 seconds are calculated. Every 400 years is overcounted: 44 minutes and 56 seconds 100 = 3 days, 2 hours, 53 minutes and 20 seconds, so every 400 years you have to remove three leap years.

Therefore, it is stipulated that "there is no leap in a hundred years, and there is an intercalary in four hundred years", that is, when the number of the year in Common D.D. is an integer hundred, although it is divisible by 4, it cannot be divisible by 400, and it is not counted as a leap year. For example, 1900 is not a leap year, while 1600 and 2000 are leap years.