A leap year is a year in which one extra day has been inserted (366 days instead of 365) at the end of February.
Leap years are needed to keep our modern day Gregorian calendar in alignment with the Earth's revolutions around the sun.
It takes the Earth approximately 365.242189 days – or 365 days, 5 hours, 48 minutes, and 45 seconds – to circle once around the Sun. This is called a tropical year, and is measured from the March equinox.
However, the Gregorian calendar has only 365 days in a year, so if we didn't add a leap day on February 29 nearly every four years, we would lose almost six hours off our calendar every year. After only 100 years, our calendar would be off by around 24 days!
Leaplings, people born on leap day, celebrate their birthdays either February 28 or March 1 in common years.
According to Guinness World Records, the only verified example of a family producing three consecutive generations born on 29 February is that of the Keogh's. Peter Anthony (Ireland) (b.1940), his son Peter Eric (UK) (b. 1964) and his grand-daughter Bethany Wealth (UK) (b. 1996) all celebrate their birthdays infrequently every four years.