Why do we have leap years?
A leap year, where an extra day is added to the end of February every four years, is down to the solar system's disparity with the Gregorian calendar. A complete orbit of the earth around the sun takes exactly 365.2422 days to complete, but the Gregorian calendar uses 365 days. So leap seconds - and leap years - are added as means of keeping our clocks (and calendars) in sync with the Earth and its seasons.
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.
What if you're born on February 29?
The chances of having a leap birthday are one in 1,461. People who are born on February 29 are referred to as "leaplings", or "leapers". In non-leap years, many leaplings choose to celebrate their birthday on either February 28 or March 1, while purists stick to February 29 for the occasion. Some suggest those born before midday on February 29 should celebrate their birthdays on February 28, while those born in the afternoon and evening of the 28th should celebrate their special day on March 1. Those born around midday are less fortunate when it comes to picking a side. About 4.1 million people around the world have been born on the 29th.