When I was a child, the happiest thing for me was the Spring Festival. Although I don't have the joyous feeling of my childhood, I still look forward to the Spring Festival, because only when the Spring Festival is coming, I will have time to return to the place where I was born and meet my relatives who I have not seen for a year.
So this time, let's take a look at the common year and leap year, how do they come about? And how to distinguish?
First, the Earth's orbit around the Sun is 365 days, 5 hours, 48 minutes and 46 seconds, not a full 365 days. How to deal with this extra 5 hours? Because if you ignore these 5 hours, then the four seasons and months cannot correspond year by year. 5 hours and 48 minutes and 46 seconds a year, then 4 years can accumulate to 23.25 hours, close to a day. So the accumulated day is added to the last day of February of the fourth year, which is February 29, which only appears every four years. So, there is one more day in this year, a total of 366 days, which is a leap year. If a person's date of birth is February 29, their birthday may only pass once every 4 years.
If one year every 4 years is a leap year and 3 years is a common year, then there should be 100 leap years every 400 years. However, the truth is that every 400 years there will be 3 fewer leap years. Because every 4 more days, it is not a full 24 hours, but 45 minutes less than 24 hours. That's 45 minutes less, and that adds up to 4,500 minutes after 100 leap years. 4500 minutes is 75 hours, close to 3 days. So, subtract these 3 days, that is, subtract 3 leap years. So the result is that there are only 97 leap years every 400 years, not 100 leap years.
So how do you tell if the year is a common year or a leap year? When encountering a whole hundred years, such as 1800, 1900, 2000, then the year must be divided by 4 or 400, which is a leap year. So, 2000 was a leap year, and 1800 and 1900 were a normal year.
If the year is not a whole hundred, such as 1987, 2016, 1833, the year should be divided by 4, so 2016 is a leap year, 1987, 1833 is a common year.
As mentioned earlier, 4500 minutes is 75 hours, so it is only close to 3 days but not the whole 3 days, 3 days is 72 hours, which is 3 hours more than 3 days.
Every 400 extra 3 hours, then 3200 years will accumulate into one day. As for how to deal with this day, with the development of science and technology in the future, there will be a more precise way.