📅 Why does February leap every 4 years?
📅 Why does February leap every 4 years?
I just found this information and wanted to get it to you before I had to wait until the next leap year.
Do you know anyone who has a birthday on February 30? How about September 31? Maybe October 32 or November 31?
No? Well, there's a good reason for that and you've probably already guessed it: those aren't even real days!
The reason February is shorter than other months comes down to the history of how we measure and divide the year.
We know that the Earth takes 365 days and just under six hours to go around the Sun. The division of those days into twelve months is a human invention to measure time. But it hasn’t always been divided that way.
In the first surviving ancient Roman calendar, there were ten months. The calendar was shaped by the agricultural year, so began in spring with March and ended 304 days later in December. There was no work to be done in the fields during the two months of winter, and the rest of days in the year were simply not counted in the calendar.
In 731BC Numa Pompilius, the second king of Rome, decided to line the calendar up with the phases of the moon. There are 12 cycles of the moon each year, so the calendar was divided into twelve months. January and February were added and the new calendar year lasted 355 days.
The Romans believed that even numbers were unlucky, so the length of the months in Pompilius’ calendar alternated between 29 or 31 days. However, the length of the calendar year meant that the final month – February – was left with only 28.
In Rome, February was linked with rituals of purification, or februum – giving it its name. During the festival of Lupercalia purification ceremonies took place to prepare buildings and people for the feasts and sacrifices of the festival. During the festival of Feralia food and gifts were brought to cemeteries, to honour the dead and keep them happy so they would not rise and haunt the living.
However, a calendar year lasting 355 days created its own problems. Because the Earth takes longer than this to go round the Sun, as years went by the months and the seasons started to fall out of alignment. So an extra month called Mercedonius was added to the calendar before the start of March.
Mercedonius was not used every year. It was added whenever it was necessary to re-align the months and the seasons. It had either 27 or 28 days, creating a year that lasted for either 377 or 378 days.
But this had unfortunate consequences for February. Mercedonius started on 24th February, cutting four days from a month that was already the shortest in the calendar. And although Mercedonius helped to link the months with the seasons, its use was unpredictable. People living far from Rome might not realise that the extra month had been added to the calendar.
Another calendar
Another new calendar tried to fix this problem. In the Julian Calendar, named after Julius Caesar and dating from 45 BCE, a year lasted 365 days.
None of the extra ten days were added to February. There were twelve months, each of which were the same length as in our calendar. To keep the calendar accurate, an extra day was added to February once every four years – a leap year.
However, an extra day each four years is actually a bit too much to correct the difference between a 365-day year and the 365 and just under a quarter days in which the Earth orbits the Sun. By the middle of the sixteenth century, the Julian calendar was out of alignment with the seasons and cycles of the year by ten days.
This led to the creation of another calendar. The Gregorian Calendar was introduced in 1582, named after Pope Gregory XIII, and is still in use today. In the Gregorian calendar, no century year can be a leap year unless it is exactly divisible by 400 – so 2000 was a leap year, with an extra day in February, but not 1900. This prevents the problems caused by the Julian calendar.
This sounds simple enough, but that ten-day error in the Julian calendar still needed to be corrected. In 1582, ten days were taken out of the calendar in countries that adopted the Gregorian calendar. This meant that the day after 4 October was 15 October – and the dates in between never existed.
Helen Parish is Professor in History at the University of Reading.-
This article is republished from The Conversation under a Creative Commons license.
https://research.reading.ac.uk/
Another explanation
Have you ever WONDERed why all the months of the year don't have the same number of days?
To solve this mystery, we must dig deep into the history of our modern calendar, which is known as the Gregorian calendar. The Gregorian calendar was a modification of the Julian calendar, which itself was a modification of the ancient Roman calendar.
The ancient Romans, like ancient civilizations before them, based their concept of the month on the Moon. Unfortunately, the lunar cycle is approximately 29.5 days, which does not divide evenly into the 365.25 days that make up a year.
As a result, the earliest ancient Roman calendars had months that were either 29 or 30 days. To make things even more confusing, the ancient Romans borrowed from the ancient Greeks to develop the idea of a 10-month calendar that left approximately 60 days unaccounted for.
For example, the ancient Romans started using a 10-month calendar in 738 B.C. that included the following months: Martius, Aprilis, Maius, Junius, Quintilis, Sextilis, September, October, November, and December. The names Quintilis through December derived from the Latin words for five through ten.
To account for the remaining 60 or so days, Januarius was added to the beginning of the year and Februarius to the end of the year during Numa's reign around 700 B.C. The calendar stayed in that order until 452 B.C. when a small council of Romans, called the Decemvirs, moved February to follow January.
Julius Caesar modified the Roman calendar in 46 B.C. to make each month have either 30 or 31 days, with the exception of Februarius, which had 29 days and gained an extra day every fourth year. Quintilis was later renamed Julius in his honor. Likewise, Sextilis later became Augustus to honor Augustus Caesar. Augustus was also given an extra day (taken away from Februarius), so that Augustus and Julius would have an equal number of days.
So the next time you're curious about why a particular month has the number of days that it does, you can thank the Moon and the ancient Romans!
From https://www.wonderopolis.org/
There you have it. This is not my writing. I took it directly from the websites above. I’m sorry I didn’t have time to edit this. I found it this morning February 29, 2024 and thought you’d be interested without waiting 4 years. Now you’re smarter than you were yesterday (except for you who already knew this).
LPM
Did you know that Leap Year does not happen EVERY 4 years? Leap Year happens on any year that is evenly divisible by 4, but not on years that are divisible by 100, with one exception. If a year is divisible by 400, it is not a leap year.