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!