Every four years an extra day is added to the Gregorian calendar.  This is the calendar that most of us use on a daily basis.  I was curious as to the history of adding a day and why it is necessary every four years.

Who Invented Leap Years? 

Roman General Julius Caesar introduced the idea over 2000 years ago.  During the Roman Empire the Julian Calendar was the only one used and he added one rule to it.    Julian calendar had only one rule: any year evenly divisible by four would be a leap year. 

This formula produced way too many leap years, but was not corrected until the introduction of the Gregorian calendar more than 1500 years later.

Why Are Leap Days Important?

Leap years are added to keep our modern day calendar in alignment with the Earth’s revolution around the sun. It takes the Earth approximately 365.242189 days –365 days, or  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!  The next Leap Day is February 29, 2016

Leap Day Traditions

A few fun traditions;

• Women Propose To Their Men – On leap day it has been an Irish tradition that the Women propose to men for marriage.
• Some area’s call it “Bachelor Days” – If a man rejects the women’s marriage proposal on a leap day he is expected to “pay a penalty” such a s a gown or money.  In European countries, especially in the upper class communities it is tradition that if the man rejects the women’s proposal he must buy her twelve pairs of gloves to hide her shame and embarrassment of not wearing an engagement ring.
• Leap Day Baby’s – For those baby’s born on this day their birthday’s are celebrated either February 28 or March 1.   

The Jewish Leap Year – is referred to as  Shanah Me’uberet, has 13 months and occurs seven times in a 19-year cycle. 

Adar – The Lucky Month

An extra month, Adar I, is added after the month of Shevat and before the month of Adar in a leap year. The month is also known as Adar Rishon or Adar Alef. According to Jewish tradition, Adar is a lucky and happy month.

The Chinese Calendar  – Adds a whole leap month to correlate with the traditional Gregorian calendar.

When is the Leap Month?

To determine a leap year, find the number of new moons between the 11th month in one year and the 11th month in the following year.

A leap month is inserted if there are 13 moons from the start of the 11th month in the first year to the start of the 11th month in the next year.

The Chinese calendar uses a solar term system that has 12 principal terms to indicate when the Sun’s longitudes is a multiple of 30 degrees. Unlike all other months, the leap month does not contain a principal term (Zhongqi).

Hope you found this informative as I have.

** Information taken from http://www.timeandate.com  http://www.timeanddate.com/date/leap-day.html