A leap year is a year in which one extra day is added to the calendar so that it is synchronized with the seasons. In other words, the earth does not orbit the sun in exactly 365 days. Other names for a leap year are a bissextile or an intercalary year. A year which is not a leap year is called a common year.
Although we generally think of a common year as 365 days, is actually 365.24190 days long. An extra day is added roughly every four years at the end of February, which is the shortest month in the year, giving February has 29 days instead of 28 days. In the Gregorian calendar, there is a leap year every year which is visible by four except for those years which are both divisible by 100 but not divisible by 400. So for example, the year 2000 is leap year while the years 1700, 1800, and 1900 were not.
Additionally, the small difference of 0.000125 days and up in a manner which causes every 8,000 years to lag approximately one full day. Logic would dictate that every 8,000 years, another additional day would be added, however by then, the vernal equinox will have changed by an unknown and unpredictable amount, so it is likely that no additional adjustment needs to be made.
The leap year was first introduced by Julius Caesar in 46 BC. In the year 10 BC however, it was discovered that the priests who were in charge of keeping the Julian calendar had been mistakenly adding leap years every three years rather than every four, and in order to correct this in error, there were no more leap years until the year 8 AD.
People who were born on February 29th are called “leaplings" or "leapers." Those people have the option of celebrating birthdays on either February 28 or on March 1.
In Gilbert and Sullivan's "The Pirates of Penzance," a pirate apprentice named Frederic signed a contract which counted his birthdays instead of the years he had been alive, and he ended up agreeing to serve the pirates until his 21st birthday, which meant until he was 84 years old.
It is perhaps a bit of irony that the day which was born in order to return order to the calendar is so frequently associated with the unnatural.
It is an old folklore that babies who are born on leap day are sickly or hard to raise. The origin of this wives tale is unknown.
It has also been said that legumes which are planted during leap year "grow the wrong way," and in Scotland the say that “leap year was never a good sheep year.”
Then there is the tradition whereupon women were granted the privilege of proposing marriage to men rather than the other way around during a leap year or specifically on leap day, depending upon the culture.
This tradition which is said to have inspired the tradition took place in 5th century Ireland with an incident which occurred, legend has it, between St. Brigid of Kildare and St. Patrick. Brigid supposedly complained about the fact that women couldn't propose to men. After some back and forth, Patrick allowed that women could do so every four years on the leap year.
Again according to legend, Brigid proposed to Patrick, and he declined. Instead, he gave her a silk gown and a kiss.
During the Middle Ages, when the tradition became popular, it is said that Queen Margaret of Scotland decreed that if a man refused such a proposal must provide the woman with a silk gown and a kiss in compensation. In Denmark, the penalty was twelve pairs of gloves, and in Finland, it was enough fabric to make a new skirt.
In order to allow men the chance to escape such a situation, the woman was required wear a red petticoat showing beneath the hem of her dress in order to "warn" the object of her affection.
In Greece, however, no such law or tradition exists, given the fact that there is a superstition in the country which says that it is bad luck to marry during a leap year, and only one out of five Greeks dare to tempt fate by doing such a thing.
Whether you're planting beans and peas; whether you're wearing a red petticoat, or running from a woman wearing one; or whether you're a Greek who is running even faster from one, enjoy the extra day this February, on Wednesday, the 29th.