Why Do We Have Leap Years? The 29-Day Phenomenon Explained

So why do leap years occur? Well Leap Days, or an extra 29th day to the month of February are added because the actual time it takes the Earth to rotate the sun is 365.2421 days. To ensure consistency with the true astronomical year, an extra day is added to the year in order to get the calendar back in sync with the movement of planet. So, every four years, an additional 24 hours is added to the month of February, creating this 29-day phenomenon and keeping the world spinning.

The idea is nothing new; in fact it dates all the way back to ancient Egypt. The Egyptians were the first to realize the need for a leap year, but it was in fact the Roman's who first brought it into practice in Europe. In 46 B.C., Julius Caesar and the astronomer Sosigenes altered the Roman lunar calendar for the solar calendar with 12 months and 365 days, as well as the leap year cycle. However, as the solar year is only .242 days longer and not .25, there are still an extra 11 minutes added to every year.

That's why in 1582, Pope Gregory XIII instituted a revised “Gregorian Calendar” in which leap years occur ever four years except for years evenly divisible by 100 and not by 400. For example, the year 1900 was not a leap year because it was divisible by 100, but not 400. Nowadays Leap Days are full of traditions all over the world (especially Europe), which include women proposing to men and Leap Year parties, amongst others.