February 29th only happens once every four years. In the Gregorian calendar, at least. And 2016 was a leap year, meaning we have 366 days this year instead of the normal 365.
Why do we have leap years?
It’s all down to the number of days it takes for the Earth to orbit the sun. We all take it as given that it’s 365 days. It isn’t. It’s actually 365.25 days. This means we have an extra quarter of a day floating around. And that has to go somewhere or the universe will implode.
That’s why we have a leap year. We simply add four quarter-days together to make a full day and plonk it on the calendar every four years.
It’s not actually as simple as that, though.
How long is a year?
I mean, really. How long is an actual year? And be accurate and precise.
The amount of time it takes for the Earth to orbit the sun is actually 365 days, 5 hours, 48 minutes, and 45 seconds.
This means that it’s not exactly 365 and a quarter days.
Basically, there is an excess of 44 minutes that need to be accounted for somewhere. About the actual length of an hour long show without all the annoying adverts.
We, therefore, subtract 3 days every 400 years to compensate for those 44 minutes.
To simplify it:
All years that are divisible by 4 have a leap year. For example, 2004, 2008, 2016, 1996, 1704.
However, if the year is divisible by 100, but not by 400, then that year will not be a leap year.
Confused yet? I am. It’s giving me a headache doing all this math.
To give an example: because of the divisible by 100 but not by 400 rule, the years 1700, 1800, and 1900, weren’t leap years. Nope, no extra day on February 29th.
In the future, the same will go for 2100, 2200, 2300, and 2500. No February 29th.
But, I’m pretty sure none of us will have to worry about making sure our calendars are correct.
So, how long is a year? Depends on who you ask.
In the Chinese calendar, the extra day in a leap year, February 29th, only occurs in the years of the dragon, monkey, and rat.