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[February 29] The One Thing Most of Us Do Not Know About Leap Years

We've all been taught that if a year is divided by 4, it's a leap year. We add an extra date to February on those years.

So if we divide the year 2022 by 4, most of us are likely to conclude that the world has come across 505 leap years so far. Unfortunately we're wrong!

Wondering why? Well, there's a special rule about counting a century year (say the year 100, 200, 300, 400, and so on) as a leap year. Most of us haven't been taught about this in our schools.

Now the folks working in IT may be tempted to open an Excel file, and look for a date formula to count the number of leap years the world came across so far. Atleast I did!

But hang on! The dates in Excel sheet start from January 1, 1900. In other words, Excel can't understand the date December 31, 1899 and all the dates before it!

And there's another fun fact. Even Excel is wrong in counting the year 1900 as a leap year.

Ok, without taking much of your time, we'll break that special rule for you right away!

In this blog post, we'll share the rule applied for a century year in order to determine if it's a leap year or not!

The rule applicable for the century years is they should be divided by the number 400 instead of 4. So the years 100, 200, 300 (though divisible by 4) are counted out, but the year 400 (which is divisible by 400) is a leap year.

Similarly, the years 500, 600, 700 are counted out, but the year 800 is a leap year! Similarly, the years 1200, 1600, 2000 are leap years, while the century years in between them are not.

Now circling back to the first question, we can conclude the world had 490 (instead of 505) leap years so far.

And BTW, the upcoming century year, 2100 is not a leap year!

This post is a part of CorpScroll's Crazy Google Searches we did post.

To be honest, we were on a quest to find the day of the week on the date January 1, 0001. But we were getting it wrong by 2 weeks and a day as we counted all the century years as leap years.

The week day of January 1, 0001 is a Monday. We look forward to share our method of calculation and conclusion on a separate post!


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