Why do we need leap year?

Just happened to think about what today is... It's leap year, we should all be jumping for joy.

The Gregorian calendar, which now serves as the standard calendar for civil use throughout the world, has both common years and leap years. A common year has 365 days and a leap year 366 days, with the extra, or intercalary day ~ designated as February 29. A leap year occurs every four years to help synchronize the calendar year with the solar year, or the length of time it takes the earth to complete its orbit about the sun, which is about 365¼ days.

The length of the solar year, however, is slightly less than 365¼ days—by about 11 minutes and 14 seconds. To compensate for this discrepancy, the leap year is omitted three times every four hundred years.

In other words, a century year cannot be a leap year unless it is divisible by 400. Thus 1700, 1800, and 1900 were not leap years, but 1600, 2000, and 2400 are leap years.