Monday, February 24, 2020

The Roman Leap Day

The only surviving sculpture of
Julius Caesar
made during his lifetime
The Romans were famously practical, and their practical engineering works are still a marvel to this day.  Looking at this, you might think that the Romans were almost modern in their approach to the world.  While that's partially right, it misses a huge part of the story, one that makes the Romans very, very foreign to modern eyes.  They were incredibly superstitious, to the point where they would refuse to fight battles if the sacrifices did not show the proper portents.  It was kind of like "everybody go back to their tents because the liver spots on these sacrificial animals were in the wrong place".

Err, or go build an aqueduct or road or something.  It's kind of like if the Massachussets Institute of Technology used Ouija boards.

Today is a great example of this.  The old Roman calendar was 355 days long.  Sharp-eyed readers will think that's ten days (actually ten and a quarter days) too short.  As a practical people, they also knew this was too short, and so they added a Leap Month every year or two.  This month was called Mercedonius, and began on this date.  The rules for the month grew over time and became enshrouded in superstition, to the extent that they were fabulously complex and Julius Caesar didn't bother to try to rationalize them in his Julian Calendar - he just eliminated the whole thing.  Just as an example, the month didn't follow February, it was embedded within it.  Caesar's simplified calendar had a 365 day year which was also wrong (but still a big improvement) and which lasted until Pope Gregory got the year changed to 365 and a quarter days - which is the calendar we have today.  We get an extra day every four years, a Leap Day, rather than the weirdness of a Leap Month.

As a weird coincidence, the ancient Roman Mercedonius was authorized each year by the Pontifex Maximus priest; the Popes are the descendants of that office, and the twitter account of the Pope is @Pontifex.  As another weird coincidence, Pope Gregory introduced his calendar on this day in 1582.

No telling if Pope Gregory used a Ouija Board in making his new calendar.  Probably not.

But Happy Mercedonius anyway!


libertyman said...

So can we measure more accurately today how long it takes to get around the sun, in order that our seasons stay the seasons they are? I guess that is why we use the system we have now.

LSP said...

Endlessly captivated by classical antiquity. So similar but totally not, like a different dimension perhaps. And of course, not Christian.

Richard said...

And Caesar was Pontifex Maximus.

Gunker said...

Caesar's calendar was 365.25 days long which was a few minutes longer than the astronomical year. These added up over the years, and by the time Gregory corrected it, the calendars were 11 days out (13 for the British who delayed adopting the Gregorian calendar due to it's popish influences)

SiGraybeard said...

Today we measure the year to such precision that we add leap seconds pretty routinely. Not every year, the last one was in 2016, because not only has the Earth's rotation been slowing for a few centuries, it's slowing irregularly.

Considering what they had to work with, they did pretty well.

As the saying goes, we see farther by standing on the shoulders of giants.

Richard said...

And the Russians didn't adopt until the Bolsheviks took over which explains why the October Revolution was always celebrated in November. I always found it interesting that the Bolsheviks went with the Pope instead of the dictator. They could have made up their own like the Jacobins did.

Will you turn off the Captcha anyway. It is dysfunctional.