Happy Leap Day!
February 29th, also known as leap day is a special date. It appears on our calendars once every four years in what is known as a "Leap Year", when the year ends with 366 days instead of the normal 365. Leap years were created to balance out the differences between our calendar and the solar calendar.
Our normal 365 day year is measured on the approximate time it takes the earth to revolve around the sun. However, the key word here is approximate - it actually takes a little longer than that - 365 1/4 days, making the calendar year slightly shorter than the "solar" year.
While it seems like a difference of a few hours, over the years it adds up. For example, after every four years, the calendar would be behind by a day and after every 100 years the difference between a solar and calendar year could add up to 25 days.
This would mean that while on a calendar year summer would be in June - for the solar calendar it would not be until a month later! If left unchecked, the timing of all our seasons could be impacted. Therefore, this system of adding an extra day started by the Egyptians and soon adopted by the Romans has worked well to re-align the two calendars every four years - and give us an extra day in the year.
For people born on this day, it means a birthday every four years. It is estimated that 1 in 1500 people are born on leap day. Currently there are less than 200,000 people in the United States and only about 4 million people around the world who celebrate their birthdays on this day.