Why is it a leap in four years, but not in a hundred years?

This is related to the Earth's orbital cycle. Using the Sun as a reference, the Earth's orbital period is 365 days, 5 hours, 48 minutes and 46 seconds, which is a return year. And we usually use a year of only 365 days, so the year is close to 6 hours, in order to make up for these 6 hours, there is an extra day in the four years, put it in February, when February has 29 days, it is a leap year.

A leap year is defined as a leap year that is divisible by 4).

This is not accurate enough, because the time difference in the year is 5 hours, 48 minutes and 46 seconds, and the actual time is less than 6 hours, so what to do, so it is stipulated that the year that is divisible by 100 and divisible by 4 at the same time is not a leap year, for example, 2000 is not a leap year.

I'm tired of playing so much, I don't know if I can make it clear.

First of all, you need to know what the purpose of a leap year is, not to say that the 4th year is like a festival to celebrate a leap year, but to correct the number of days, which is explained as follows.

Leap years are marked by the fact that the Earth orbits the Sun with a period of 365 days, 5 hours, 48 minutes and 46 seconds (conjunctive days), which is one.

Tropical year. The common year of the Gregorian calendar is only 365 days, which is shorter than the return year, and it accumulates about one day every four years, and this day is added to the end of February (that is, February 29), so that the length of the year becomes 366 days, and the year is a leap year.

It should be noted that the current Gregorian calendar is based on the Romans"Julian calendar"Adapted. Since it was not understood at the time that there was an extra number of days to be counted each year, from 46 B.C. to the 16th century, a total of 10 days were accumulated. For this reason, Pope Gregory XIII at the time artificially designated October 5, 1582 as October 15.

and began a new leap year rule. That is, if the Gregorian calendar year is an integer hundred, it must be a multiple of 400 to be a leap year, and a multiple of 400 is a common year. For example, 1700, 1800 and 1900 are common years, and 2000 is a leap year.

Thereafter, the average annual length is days, with a deviation of 1 day in about 4 years. According to a leap year every four years, there are an average of more days per year, and after 400 years there will be about 3 more days, so every 400 years there will be a decrease of three leap years. The calculation of leap years boils down to what is commonly said:

a leap in four years; There is no leap in 100 years, and then in 400 years.

Upstairs Mickey Mouse's statement is already very detailed, which is based on the Chinese calendar's annual rotation of the earth around the sun, and only the leap month is to correct the error.

This is to make up the time of the year, so that the time of the earth's revolution around the sun and the year can be aligned.

Leap years or leap months are the wisdom of the ancients. The conclusions reached by the ancients after a long period of observation and research always have their truth.

This is because the actual time it takes for the Earth to orbit the Sun is 365 days, 5 hours, 48 minutes and 46 seconds. In a normal year, 365 days are counted, so that every four years is less than 5 hours, 48 minutes and 46 seconds 4 = 23 hours, 15 minutes and 4 seconds. Therefore, an additional day is added to February of the fourth year, which is called a leap year (366 days), which is the principle of "one leap in four years".

The 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 will be no leap in 100 years, and there will be an intercalation in 400 years".

In general, in the Gregorian calendar year, the leap year that can be divisible by 4 is a leap year, but the Gregorian calendar year is an integer hundred, and it should be divisible by 400 to guess that it is a leap year, such as 2100 is a common year and 2000 is a leap year.

365 days in a normal year and 28 days in February; Leap years are 366 days and February is 29 days. February in leap years has one more day than February in ordinary years. So where does the extra day in leap years come from? This is an interesting question that teachers should be aware of.

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 revolve around the Sun is 365 days, 5 hours, 48 minutes and 46 seconds.

For convenience, we calculate the normal year as 365 days, which is actually 5 hours, 48 minutes and 46 seconds less, and the difference in four years is 23 hours, 15 minutes and 4 seconds, which means that four years are nearly one day less. So every four years a leap year is prescribed, and this day is added to February of the leap year to make up for the undercounted time, also called"a leap in four years; "。

According to the above description, every four years there is a leap year, but the time is not a full 24 hours, so every four years a leap is counted an extra 44 minutes and 56 seconds. In this way, every 100 years is an extra 18 hours, 43 minutes and 20 seconds, and nearly one day. Therefore, by the full 100 years of the Common Era, this year is not counted as a leap year, so as to offset the time of overcounting, it is called"A hundred years without leaps"。

According to the above calculation of 100 years without leap, there are 5 hours, 16 minutes and 40 seconds more for each hundred years, so that every 400 years there is an extra 21 hours, 6 minutes and 40 seconds, which is almost another day. Therefore, when the year of the Common Era is a multiple of four hundred, the year is again a leap year, and it is called"Four hundred years and a leap"。Here it is"There is a leap in four years, no leap in a hundred years, and a leap in four hundred years"The truth.

The year 2000 is a leap year, and the year 2100 is not a leap year.

The same goes for it"Four hundred years and a leap"In fact, another 2 hours, 53 minutes and 20 seconds were lost, and after eight four hundred years (3200 years), another 23 hours, 6 minutes and 40 seconds were lost. Therefore, when the AD year is a multiple of 3200, a leap is subtracted (i.e., 3200 and 6400 AD are not leap years). In this way, the error between calculating leap years and the actual time of revolution is very small.

How to determine leap years.

1. Non-integer 100 years: those that can be divisible by 4 are leap years. (e.g. 2004 is a leap year, 2001 is not a leap year);

2. Whole 100 years: 400 divisible is a leap year. (e.g. 2000 is a leap year, 1900 is not a leap year);

3. For a year with a large value: if the year is divisible by 3200 and divisible by 172800, it is a leap year. For example, 172,800 is a leap year, and 86,400 is not a leap year (because although it is divisible by 3200, it is not divisible by 172800).

6 minutes and 40 seconds. Therefore, when the AD year is a multiple of 3200, a leap is subtracted (i.e., 3200 and 6400 AD are not leap years). In this way, the error between calculating leap years and the actual time of revolution is very small.

Four years, a leap year, a hundred years are not moist, and four hundred years are moist, which means that the year is a multiple of 4, a multiple of 100 is not a leap year, and a multiple of 400 is a leap year.

Four years are intercalary, a hundred years are not intercalary, and four hundred years and intercalary means that the previous part of the year is a multiple of 4 is a leap year, a multiple of 100 is not a leap year, and a multiple of 400 is a leap year. This is the law followed by the determination of leap years in the Gregorian calendar.

The calculation law of leap months in leap years in the lunar calendar:

One leap in the year, two leaps in the fifth year, seven leaps in the 19th year; The lunar calendar is basically a cycle of 19 years, corresponding to the same time in the Gregorian calendar. For example, May 27, 2001, May 27, 1982 and May 27, 1963 in the Gregorian calendar are all the fifth days of the fourth month of the leap month.

2. The month to which the leap month is added is inferred from the rules of the lunar calendar, and is mainly determined according to the correspondence with the 24 solar terms of the lunar calendar; The number of leap months in the lunar calendar is the same as the number of days in a normal month, which is 29 or 30 days. The so-called leap year in the lunar calendar is only called leap year and leap month, and the Gregorian calendar also has the title of leap year.

The principle of leap years:

1. Leap years are divided into ordinary leap years and century leap years, which are established to make up for the time difference between the number of days in the year and the actual revolution cycle of the earth caused by the artificial 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).

2. Where there is a leap day (February 29) in the solar calendar, the leap (the year is more than the leap. The difference in time between the lunar calendar and the return year). Note that there is no direct correlation between leap year (noun in the Gregorian calendar) and leap month (noun in the lunar calendar), the Gregorian calendar 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, such as 2017 is a common year, and the lunar calendar has a leap month and a leap June.

Classification of leap years:

1. Ordinary leap years.

If the Gregorian calendar year is a multiple of 4 and is not a multiple of 100, it is a leap year (such as 2004, 2020, etc. are leap years).

2. A leap year of the century.

Gregorian calendar years are whole hundreds. <>

The reason why there is a leap year every four years and no leap year in a hundred years is: a leap year has a total of 366 days, a year that is divisible by 4 in an ordinary year but not divisible by 100 is an ordinary leap year, and a century year that is divisible by 400 is a leap year in the century. The earth revolves around the sun, and one rotation is 365 days in a year, 5 hours, 48 minutes and 46 seconds, and in ordinary years, it is calculated according to 365 days, and every 4 years is less than 4 5 hours, 48 minutes and 46 seconds, which is equal to 23 hours, 15 minutes and 4 seconds, which is a little less than the time of a day, close to one day, so one day is added every 4 years, therefore, a leap year should be prescribed every four years.

Although 23 hours, 15 minutes and 4 seconds are counted as a day with only 44 minutes and 56 seconds, which is not much, if 400 years have passed, it adds up to 3 more days, so it should be reduced by 3 days in these 400 years. Grinding and knowing this blind rubber disappearing is "one leap in four years, no leap in a hundred years, and another leap in four hundred years".

Leap year is a term in the Gregorian calendar, 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. The year in which the time difference is made up is a leap year.

There are 366 days in a leap year, a year that is divisible by 4 but not 100 in an ordinary year is an ordinary leap year, and a century year that is divisible by 400 is a leap year.

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 every four years, so the fourth year adds one day at the end of February, so that the length of the calendar year of that year is 366 days, and this year is a leap year. There are 97 leap years in the current Gregorian calendar every 400 years.

According to a leap year every four years, the average number of days per year is to be counted out, so that after 400 years, about 3 days will be calculated. Thus three leap years are reduced every 400 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.

This is what is commonly said: every four years, no leap in a hundred years, and another leap in four hundred years. For example, 2000 is a leap year and 2100 is a common year.

It is a year for the earth to revolve around the sun, and it is a day for the earth to revolve in one circle. The time of year is not an integer number of days (this is a natural occurrence, it would be strange if it were an integer number of days), but about days. For this reason, the beginning of the next year should be about a day earlier than the previous year, so that 10 years in advance, 100 years in advance, 24 days in 100 years, after a few hundred years, the relationship between seasons and months will be reversed, which will bring inconvenience to people's lives, so it is necessary to use leap years to solve this problem.

Add one day every four years, 366 days in a leap year, and the beginning of the next year will roughly return to the original point.

Since there will still be a difference in leap years alone, it is necessary to use a hundred years without a leap year and a leap year in four hundred years to make a more precise balance.

Huhu

Reason: The earth revolves around the sun for a year, to be precise, a year is actually 365 days, 5 hours, 48 minutes and 46 seconds. If a year is calculated as 365 days, it will be 6 hours less in that year, and 24 hours less in four years, that is, 1 day less.

Therefore, every four years an additional day is added, and this day is added in February, which is called a leap year.

The accurate time of the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds, which is counted as 365 days and 6 hours.

For example, Example 1: 1996: 1996 4=499 1996 is a leap year;

Example 2: 2000: 2000 400 = 5, 2000 is a leap year;

Example 3: 2100: 2100 400=, 2100 is not a leap year.

It has to do with the cycle of the Earth's autobiographical revolution. Because they are not whole numbers, they have to be made up at certain intervals.

A leap year is a noun in the Gregorian calendar, a leap year that is divisible by 4 but not by 100, or a year that is divisible by 400.

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, 31, 30, 30, 31, 31, 30, 31, 30, 30, 30 and 31 from January to December).

Any year in which there is a leap day (29 days in February) in the solar calendar; Leap more (more than the year is intercalated. The difference in time between the lunar calendar and the return year). Note that there is no direct correlation between leap years (nouns in the Gregorian calendar) and leap months (nouns in the lunar calendar), which are only divided into leap years and peaceful years, with a common year having 365 days and a leap year having 366 days (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).