In case you have not heard, today is Leap Year Day! Almost every 4 years we get the chance to celebrate this day! Why do you ask? It takes some understanding of our solar system and time to figure out why a leap day exists.
The way we measure time on Earth is a bit complicated. Years are measured by the length of time it takes our planet to orbit the sun. We call this a “solar” year. The precise measure of a solar year is 365.24219 days. Those numbers at the end of the decimal point add up. Without any sort of adjustment for the extra quarter of a day, seasons as we know them would eventually become very different. Winter would feel like summer and Summer would feel like Winter!
In 1582, Pope Gregory XIII established the Gregorian calendar and introduced the century rule.
“If a leap year falls on a century, a year ending in double zeroes, you only add a leap day if it’s divisible by 400,” physicist Judah Levine, a man the Washington Post once dubbed “the nation’s timekeeper” says. “For that reason 1900 wasn’t a leap year but 2000 was.”
According to the rules set forth in the Gregorian calendar leap years have occurred or will occur during the following years: