This is the one extra day inserted, or intercalated, at the end of February during leap years. These leap days are needed to keep our calendar in alignment with the earth's movement around the sun.
An astronomical year, the time taken for the Earth to completely orbit the Sun, is about 365.242 days. Always using a calendar with 365 days would result in a loss of about six hours every year.
This is not as inconsequential as it seems. After 200 years, a 365 day calendar would be more than 48 days ahead of the seasons, which could get confusing. Eventually the coldest day of winter could be the fourth of July.
By adding a leap year roughly every fourth year, our "Gregorian" style calendar aligns with the seasons much more accurately.So all in all, leap days are helpful, but February 29 can still an issue for some.
For example, when do people, born on February 29 celebrate their birthdays? Imagine you get a birthday cake once every 4 years. Bummer.Instead of waiting for the next February 29, these "leap-year" babes , also known as leapsters, typically celebrate their day on February 28. Some even attend the Worldwide Leap Year Festival to celebrate when leap days come around.