What is the leap year actualy for?

The time it takes for the earth to rotate is a year. But it is not exactly a year, it is more like 365.25 days. (Generally). So, to make up the time, we add one day every four years. Wikipedia also has a nice article on this.

happy 29th
does anyone do anything different on 29th february? to make it special etc.
or does anyone celebrate their birthday today?

A leap year, also known as an intercalary year, is the one containing an extra day, normally February 29th, although this varies in certain calendars. In the Gregorian Calendar, which is used by most of the world, a leap year occurs every four years or 97 years out of every 400. This is done as a way to keep seasons, astronomical events, and time differences in sync. Without leap years, the Gregorian calendar would lose veracity in just over a hundred years, leading to time differences between day and night, and moving the equinox early. The Gregorian method is by far the most accurate way to creating leap years. By adding a 29th day in all years divisible by 4 (except for years ending in -00), the Gregorian calendar will fall behind only one day every 8000 years.
http://www.wisegeek.com/why-do-we-have-leap-years.htm

Using a calendar with 365 days every year would result in a loss of 0.2422 days, or almost six hours per year. After 100 years, this calendar would be more than 24 days ahead of the season (tropical year), which is not desirable or accurate. It is desirable to align the calendar with the seasons and to make any difference as insignificant as possible.

The year 2008 is a leap year. If you look at a 2008 calendar, you will see that February has five Fridays–the month begins and ends on a Friday. Between the years 1904 and 2096, leap years that share the same day of week for each date repeat only every 28 years. The most recent year in which February comprised five Fridays was in 1980, and the next occurrence will be in 2036. February 29, the leap day, has been associated with age-old traditions, superstitions and folklore.
http://www.timeanddate.com/date/leapyear.html

We need leap years to correct the calendar because the Earth’s orbit isn’t exactly 365 days long. It is 365 days six hours, eleven minutes and about 15 seconds. The difference which mounts up each year is corrected by adding an extra day at the end of February, every four years.
Even this is only a partial solution. Having a leap year brings the calendar back by 45 minutes. This gets corrected at the end of a century by missing out the leap year. It doesn’t end there. This corrects the calendar by six hours too much. So to fix this every fourth end of century ‘is’ a leap year.
A leap year is always divisible by four unless it is the last year of the century. The last year of a century is a leap year if it is divisible by 400. Therefore 2000 was a leap year, but 1900 was not.
http://www.blurtit.com/q997158.html

It’s when the girl is suppose to ask the guy to marry her.

It takes 365.25 ( 365 1/4) days in a year to revolve around the sun. Every 4 years we add a day to February to even it out.