Introduction to the leap year of the gregorian calendar

<h1 class="pgc-h-arrow-right" data-track="1" > an introduction to the leap year of the solar calendar</h1>

There are 365 days a year.

There are 366 days a year.

These two sentences are correct nonsense, because this is the truth that most people know, but if you ask more, then which year is 365 days, which year is 366 days, probably most people can still answer, the year is divided into a leap year, a flat year is 365 days, and a leap year is 366 days. Keep asking, so how to judge whether a year is a normal year or a leap year? At this time, there may be some people who can't accurately answer the standard answer, maybe most people remember only one sentence, what can be divisible by 4 is a leap year, but in fact, this sentence is faulty, because all leap years can be divisible by 4, but not as long as all years that can be divisible by 4 are leap years.

The exact definition should be:

One of the following two criteria is a leap year:

A. All years that can be divided by 400 are leap years;

B. All years other than A that can be divisible by 4 but not by 100 are leap years;

Of course, the ancient Chinese also summed up such a law: one leap in four years, not moist for a hundred years, and four hundred years for another leap.

In addition, it should be emphasized that the leap year mentioned in this article is the leap year of the solar calendar, which is now the Common Era chronology. There is also a definition of leap year in the Chinese lunar calendar, but the Chinese lunar leap year is more complicated and is not introduced in this article.

Back to the AD chronology, the year of the AD is determined according to the time of the Earth's orbit around the sun, a long time ago, our level of science and technology could not accurately define the accurate time of the Earth's orbit around the sun, but through years of observation, it was found that the time of the Earth's orbit was a little more than 365 days, but a little less than 366 days. With the progress of science and technology, posterity has concluded that the earth's orbit is 365 days at 5:48 minutes and 46 seconds. The data I've collected so far doesn't find who first defined the time, so I can't pay tribute to the scientist who defined the exact time of year for the first time. It is precisely because the transit time is 365 days, 5 hours, 48 minutes and 46 seconds, so there is a definition of four years and one leap, one hundred years without leap, and four hundred years again.

Of course, if we define the time of year, then the four seasons of a year are divided into spring, summer, autumn and winter, and according to the four-part division method, it is easy to determine the time of a season of about 91.3 days.

For the leap year of the Gregorian calendar, again express the expression defined in this article:

Of course, if you can remember four years of one leap, a hundred years of no leap, four hundred years of leap years, then you can accurately define and answer the leap year.

Astronomy and history are intrinsically linked, and physics is also closely linked to astronomy, which is the definition of a leap year in the solar calendar.

Thanks for reading! (After this article, the public account "Taste of Fruit and Fruit" and the headline number "Duan Yuan" were suspended for 7 days, thank you for reading!) ）

June 24, 2021