2008 is a Leap Year, which means we're going to have an extra day in February to enjoy. So why do we need to add this day every four years? Well, when the Earth makes its annual trip 'round the sun, it doesn't take exactly 365 days. It's a little more like 365 and 1/4 days. Because of this, every four years our calendar falls a day behind the solar year. To remedy this, we catch ourselves up by adding an extra day to the month of February every four years. If we didn't, in 100 years the solar year and calendar year would be 25 days apart. We can't have that, or eventually our seasons would not match up with the months we currently associate them with.
Despite this necessary adjustment, it is not exact either. Every now and then we have to skip a regularly scheduled leap year. This happens during specific century years. Century years are not leap years unless they can be evenly divided by 400. The years 1700, 1800 and 1900 were not leap years, but 1600 and 2000 were. The reason we skip those years is because the exact amount of time for the Earth to circle the sun is slightly less than 365 and 1/4 days. If the leap day wasn't skipped on those century years, we'd actually get ahead of the solar year by a day.
As you can see, it takes a little finagling to match the calendar year up with the solar year. But it all seems to work out well in the end! As it stands, it takes 3300 years for the calendar year and the solar year to become "off" from each other, and then it's only by a day.
Some more fun facts about Leap Year:
~The exact amount of time it takes for the Earth to rotate around the sun is 365 days, 5 hours, 48 minutes, and 46 seconds.
~Egyptians were the first people to add a leap day every four years. However, the Romans were the first to choose February 29th as the official date.
~The year 2008 has five Fridays in February. Between 1904 and 2096, leap years with the same day of the week for each date repeat every 28 years. The last time February had five Fridays was in 1980 and the next time will be in 2036.
~Sweden (and Finland) had a "double" leap year in 1712, because two days were added to February. That year there was a date February 30, 1712. This was done because the leap year in 1700 was dropped, and Sweden's calendar was not synchronized with any other calendar. By adding an extra day in 1712, they were back on the Julian calendar.
~In ancient times, it was very usual to have lunar (moon) calendars, with 12 and/or 13 months every year. To align the calendar with the seasons the 13th month was inserted as a "leap month" every 2-3 years.
~Your chances of being born on a leap day are approximately 1 in 1500. There are about 187,000 people in the US and 4 million people in the world who were born on Leap Day.