Raleigh, N.C. — WakeMed welcomed 13 leaplings into the world Friday – babies who will see their Feb. 29 birthday roll around every four years.

Hospital workers gave each baby a froggie hat to celebrate their unique birthday.

The chances of being born on Feb. 29 is about 1 in 1,500, but approximately 4 million leaplings worldwide succeeded in defying those odds, according to the Honor Society of Leap Year Day Babies.

The Carolina Hurricanes' Cam Ward celebrated his sixth birthday today. The goaltender, though, was born 24 years ago.

In the Gregorian calendar, years are actually 365.25 days long, so every four years, an extra day is inserted at the end of February. That keeps the months in sync with the seasons.

Two criteria mark exceptions to that rule: If a year is divisible by 100 (such as 1800 or 1900), it is not a leap year. However, if a century year is also divisible by 400, it is a leap year.

The year 2000 was the first time that third criterion got to be applied.