What are Leap Years and Why do We Have them?

Kenneth Lee, Contributor

What are Leap Years
Around every four years, we have a special leap year. Leap years have an additional day added on to them called a leap day. Compared to a usual 365 days in a common year, leap years contain 366 days. This extra leap day is added onto the shortest month of the year as February 29th.

Why We Need Leap Years
The reason we need leap years is because the amount of time it takes the Earth to orbit around the Sun is not exactly 365 days. The amount of time it really takes the Earth to orbit the Sun is 365 days, 5 hours, 48 minutes, and 46 seconds, or 365.2422 days according to NASA. This is called a tropical year. As time goes on if we do not utilize leap years, the seasons will start to pull away from our calendar. By adding another day to our calendar every four years, we can keep our calendar up to speed with the seasons.

How to Identify Leap Years
You can find out if a year is a leap year by dividing it by four. If the quotient is a whole number, that year is a leap year. For instance, 2020 was a leap year because 2020 divided by 4 is 505. There is no remainder and it divided out evenly.

There is another problem, however with having a leap year every four years. According to the National Air and Space Museum, “Some simple math will show that over four years the difference between the calendar years and the sidereal year is not exactly 24 hours. Instead, it’s 23.262222 hours. … By adding a leap day every four years, we actually make the calendar longer by over 44 minutes.” This will eventually do the same thing as having no leap years and cause the seasons to not align with our calendar, albeit over a longer period of time. To counteract this, there is another rule for counting leap years. Every year divisible by 100 that is not also divisible by 400 is not a leap year. For example, 2000 was a leap year because it is divisible by 400, but the years 2100, 2200, and 2300 wouldn’t be leap years.

Fun Facts
Leap years got their name because when we have a leap year, we skip over two days instead of one. As an example, Christmas on 2018 was Tuesday, Christmas on 2019 was Wednesday, but Christmas on 2020 was on Friday. We “leaped” over a day and skipped to Friday which is how leap years got their name.

Women also often choose February 29 to propose marriage to men. It has traditionally been a day that women could propose to men which has been how it works in many cultures. Some cultures also consider this day as unlucky. In Greece, getting married on February 29 is not advised.

Leap years stabilize our calendar and seasons to make sure that they don’t split apart. Although leap years are not hard to understand, they are undoubtedly very helpful additions to our lives.