Here are some fun facts about Leap Years
What is a leap second?
Leap years are not directly connected to leap seconds, but both are for the purpose of keeping the earth's rotations in line with our clocks and calendars.
Leap seconds are added to bring the earth's rotation into line with atomic time. A leap second was added at the end of June last year, when immediately before midnight dials read 11:59:60.
Atomic time is constant, but the Earth’s rotation is gradually slowing down by around two thousandths of a second per day.
Leap seconds are therefore crucial to ensuring the time we use does not drift away from time based on the Earth's spin. If left unchecked, this would eventually result in clocks showing the middle of the day occurring at night.
The extra second can sometimes cause problems for some networks which rely on exact timings. When a last leap second was added in 2012 Mozilla, Reddit, Foursquare, Yelp, LinkedIn, and StumbleUpon all reported crashes and there were problems with the Linux operating system and programs written in Java.
Why does the extra day fall in February?
All the other months in the Julian calendar have 30 or 31 days, but February lost out to the ego of Roman Emperor Caesar Augustus.
Under his predecessor Julius Caesar, February had 30 days and the month named after him - July - had 31. August had only 29 days.
When Caesar Augustus became Emperor he added two days to 'his' month to make August the same as July.
So February lost out to August in the battle of the extra days.
Technically, a leap year isn't every four years
The year 2000 was a leap year, but the years 1700, 1800 and 1900 were not.
There's a leap year every year that is divisible by four, except for years that are both divisible by 100 and not divisible by 400.
The added rule about centuries (versus just every four years) was an additional fix to make up for the fact that an extra day every four years is too much of a correction.