Leap Day happens every four years on Feb. 29, and this year it is being celebrated on Wednesday.
A solar year consists of 365 days, 5 hours, 49 minutes, and 16 seconds - or about 365.25 days. To account for the extra time and keep the calendar on par with the sun's rotation, Leap Day occurs.
The event takes place during the shortest month of the year and brings another day to the Juian/Gregorian calendar, which we use to count our days, adding 24 full hours to the Leap Year.
If not for Leap Day adding extra time, the calendar would be one day out of sync with the seasons. After 30 years the calendar would be about a week off, and after 100 years it would be nearly a month off.
Leap Day has taken place for over 2,000 years. The 365-day calendar was invented by Julius Caesar, but it was his astronomer, Sosigenes, who deserves credit for adding the extra day in February every four years.
The quadrennial event is observed at Disneyland in California as well as the Magic Kingdom in Florida, where "One More Disney Day" allows tourists to roam the parks for a full 24 hours. The theme parks will be open from 6 a.m. Feb. 29 to 6 a.m. March 1.
For those rare people born on Leap Day, the day marks the opportunity to enjoy their true birthday. Nearly five million "leapers" world-wide share Feb. 29 as a birthday, although computer programs sometimes refuse to recognize the date, according to Reuters. Facebook blocked users from entering Leap Day as their birthdate, but has since changed its settings.
Also, many people take full advantage of the extra 24 hours by doing something special. On Twitter, users are posting they will do with their extra day.
"Happy Leap Day yawl! What kind of mischief are we getting into today," posted YourDailyWagon. "Me, I'll be completing my quest to answer ALL my emails. You?"
"Just realized that there are 366 days to have fun this year instead of the usual 365," wrote Monica.
Twitter user Renee had a suggestion for the special day, writing, "Be fearless today, not like a daredevil but fearless by faith that all will work out for the best. Happy Leap Day."
"Leap Day #SpontaneousDanceParty," wrote Coco-Cola's Twitter account. "RT if you're in!"
Also on Leap Day, people can enjoy the 2010 movie "Leap Year" starring Amy Adams and Matthew Goode. The film touches on the Irish tradition that a man who received a marriage proposal on a leap day must accept it.