A friend of mine told me his birthday was coming up. He told me it was his 15th. “What?” I thought. He’s older than me. He then told me his birthday was on February 29. Duh! Now that makes sense. Leap Years!
I know we have “leap years,” but I could not actually remember why. Maybe I am 60, but not quite yet. Anyway, I cranked up the “Google Machine” to see what I could find. As with any Google search, you can quickly go down a rabbit hole. I guess I should have asked ChatGPT to write this blog. It would have been easier. However, I digress.
What are “Leap Years”?
Yikes, are there lots of definitions out there. Here is what Wikipedia says. So as not to get too technical, during a leap year an additional day (or month) is added to the calendar compared to a typical or common year. The reason is to keep the calendar in sync with astronomical events. Plus, it depends on what calendar is used.
For example, I remember reading one time that the old Jewish calendar had 13 months in certain years. Jewish months ran from new moon to new moon, or roughly 30 days. Apparently, they used a 19-year Metonic cycle where the thirteenth month was added during the 3rd, 6th, 8th, 11th, 14th, 17th and 19th years. From what I could find, this was started by Hillel II around 359. Interesting.
Modern “Leap Years”
Obviously, most of the world as we know it does not use the Jewish calendar. So where did modern leap years come from? It all goes back to Julius Caesar. Maybe it’s not so modern.
In 46 BC, Julius Caesar decreed the Roman calendar would change from a 355-day lunar year to a 365-day solar year. Sound familiar? The new Julian calendar had twelve months of arbitrary length beginning on January 1.
Caesar’s decree also introduced leap years. Adding an extra day every four years allows the calendar to stay in sync with Earth’s actual orbit and not have our seasons drift. Roughly, but we’ll get to that. The Julian calendar chose February 29 as the “extra” day. Good for my friend.
Everyone, or most everyone, knows that the earth’s orbit around the sun is not exactly 365 days. The orbit is 365 days and change. For the sticklers out there, it actually takes 365.24219 days or 365 days, five hours, 48 minutes, and 56 seconds. Adding the extra day makes the calendar ~44 minutes longer causing seasons to drift. So, how was this slight discrepancy compensated for?
The Pope Comes to the Rescue
By the 16th century, a discrepancy of ten full days had accumulated. In 1582, Pope Gregory XIII updated the Julian calendar. Leap years every four years were retained but with the exception that only those century years with a number divisible by 400 were to be counted as leap years. For example, leap years were skipped in 1700, 1800, and 1900, but not 2000. If you are alive in 2100, you will have no leap year.
Pope Gregory XIII also omitted 10 days from the 1582 calendar, so that the day after October 4 became October 15. This Gregorian calendar is generally used in most parts of the world.
So there you have it, “leap years” explained
The topic of “leap years” is backed by gads and gads of information. The “Googe Machine” told me so. It is impossible to cover all details in a short blog. Any dicrepancies or inaccuracies are purely the fault of Danny Boesing. He gave me some of the source information.
Of course, I am kidding. Danny is a good friend and a more informed historian than me. Any discrepancies on the topic are purely my own.
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