A Little Leap Year 101

The 365 days of the annual calendar are meant to match up with the solar year. A solar year is the time it takes the Earth to complete its orbit around the Sun—about one year. The actual time it takes for the Earth to travel around the Sun is 365 days, 5 hours, 48 minutes, and 46 seconds. So the calendar and the solar year don't completely match.
After four years the four extra quarter days make the calendar fall behind the solar year by a day. Over a century, the difference would be 25 days!

The Egyptians were the first to add a leap day once every four years. Later, the Romans adopted this solution designated February 29 as the leap day.

The exact length of a solar year is 11 minutes and 14 seconds less than 365 ¼ days. So, even if you add a leap day every four years, the calendar would still overshoot the solar year by 11 minutes and 14 seconds per year. After 128 years, the calendar would gain an extra day.

Calendar Correction, Part II
The creators of our calendar (the Gregorian Calendar, introduced in 1582) omitted leap years three times every four hundred years; a century year is not a leap year unless it is evenly divisible by 400. This rule manages to eliminate three leap years every few hundred years. Now the calendar year and the solar year are just about a half a minute off. It takes 3,300 years for the calendar year and solar year to diverge by a day.

Leap Year Traditions/Stats
When the rules of courtship were stricter, women were only allowed to pop the question on one day every four years. That day was February 29th.
In the United States, some people have referred to this date as Sadie Hawkins Day with women being given the right to run after unmarried men to propose.
There is a Greek superstition that claims couples have bad luck if they marry during a leap year. Only 0.0684% of the world's population are Leapers (born on Leap Day).