as you know usually the month of February is 28 days long, but this year February has 29 days. Well, every four years we get an extra day in February. Isn't that great? :-)
A year with an extra day in February is called a leap year and it is down to the Gregorian calendar's disparity with the solar system. 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.
You might ask a question - what if someone is born on the 29th February? Do they celebrate they Birthday every four years? That wouldn't be very nice, don't you think so? Well, about 4.1 million people around the world have been born on the 29th. Some of them celebrate their Birthdays on the 28th, some on the 1st March, some every four years (well, they can feel 4 times younger than the rest of us :-) ) - I guess it's just a personal choice.
Leap years are also marked as a time for women to propose to men. In Ireland and Britain, it is a tradition that women may propose marriage only in leap years. While it has been claimed that the tradition was initiated by Saint Patrick or Brigid of Kildare in 5th century Ireland, this is dubious, as the tradition has not been attested before the 19th century. Others argue that the tradition of women proposing on this day goes back to the times when the leap year day was not recognised by English law. Under this theory, if the day had no legal status, it was acceptable to break with the convention of a man proposing.
In Finland, the tradition is that if a man refuses a woman's proposal on leap day, he should buy her the fabrics for a skirt :-)
Have you seen a movie with Sandra Bullock called 'The Proposal"? She proposed to Ryan Reynolds in the movie. She gets down on her knees and proposes like a man suppose to do. There is also a movie called 'Leap year' and it's about Anna Brady who plans to travel to Dublin in Ireland to propose marriage to her boyfriend Jeremy on Leap Day, because, according to Irish tradition, a man who receives a marriage proposal on a leap day must accept it. It is a typical romantic comedy, you may like it, so check it out if you fancy watching it.