Who invented Leap Years?
Julius Caesar introduced Leap Years in the Roman empire over 2000 years ago, but the Julian calendar had only one rule: any year evenly divisible by 4 would be a leap year. This led to way too many leap years, but didn't get corrected until the introduction of the Gregorian Calendar more than 1500 years later.
Which Years are Leap Years?
In the Gregorian calendar 3 criteria must be taken into account to identify leap years:
- The year is evenly divisible by 4;
- If the year can be evenly divided by 100, it is NOT a leap year, unless;
- The year is also evenly divisible by 400. Then it is a leap year.
The year 1600 was a leap year. The years 1700, 1800, 1900 were not leap years. However, the year 2000 was a leap year. The years 2100, 2200, 2300 will not be leap years. The year 2400 will be a leap year. The year 2500 will not be a leap year.
But Why??Because of the following reasons
It takes the Earth approximately 365.242199 days – or 365 days, 5 hours, 48 minutes, and 46 seconds – to circle once around the Sun. This is called a tropical year. So we are 5 hours, 48 minutes, and 46 ahead than calender, this makes after four years.........
We found that we are ahead 23 hours, 15 Mins and 4 Seconds. And we count it as one day(24 hours) and this makes February 29 days instead of 28 days.
Now notice that it also got some error since we are considering 23 Hours 15 Minutes and 4 seconds as a day. So calendar now ahead by..
From the above we can see that the calendar is now ahead by 0 hours, 44 minutes and 56 seconds after each four years to make an extra days(February -29). So for 1 year the calender is ahead by 0/4 = 0 years, 44/4=11 minutes and 56/4=14 Seconds. And for 100 years…
After 100 years, As the calendar is ahead by 18 hours, 43 Minutes and 20 seconds So don't count the 100 years as the leap year, though it is divisible by 4
It has also a problem!
Since calendar was ahead by 18 hours, 43 Minutes and 20 seconds we give to the calender 24 hours(By letting February in 28 days). Again we are ahead by ...6 hours 17 Minutes and 40 seconds...
This causes after 100 years, what will happen after 400 years!!
So after 400 years we are ahead by 25 hours 10 minutes and 40 seconds This makes the 400th a leap year.
You may ask that we are still ahead by 1 hour 10 minutes and 40 seconds. Yeah that's right! But this has trivial effect on tropical year as it divide among each year of 400 years!!! Gotcha??
Here the C Program to find Leap year