Roman calendars!

Today you get to learn about Roman calendars!

The calendar already had 12 months when our boy Julius got to it. The ten-month calendar was the traditional Roman calendar dating back at least to the founding of Rome; it started with March (Mensis Martius) and ended with December (Mensis December); each month alternated 30 and 31 days, with about 50 days of intercalary days at the end of the year (between Saturnalia and the beginning of March). "Intercalary" means what you think it does; they didn't have a month associated with them and were just sort of there. Moreover, the old Roman calendar called for a year of 360 days. This was not particularly clever of them.

When the last of the Tarquins was overthrown and the Roman Republic began, the Romans decided that the Greeks had a pretty good idea with their lunar calendar, so they borrowed it. The Greek calendar had 29.5-day lunar months and so alternated between 29 and 30 days per month; the year was 368 days long and required intercalary days every four years to get things back to where they were supposed to be. The Romans didn't want to get rid of their old calendar entirely, though, so they sort of haphazardly slapped 31-day months into the calendar, added two new months in at the new beginning of the year called Mensis Ianuarius and Mensis Februarius, and had a 23-day intercalary month right after them to keep things nice and adjusted.

This was MORE clever of them than the previous calendar had been, but still not particularly clever. Intercalary days are a pain in the ass.

Also, those two new months? Added around 500 BCE, more than 400 years before our boy Julius was born.

46 BCE rolled around and Julius noticed that the calendar, although it was more accurate than the old calendar, had still drifted about eighty days off course, with the end of the calendar year happening at the beginning of autumn. So he said, "look, fuck the Tarquins, fuck the Greeks, this is stupid, let's fix it." His proposal added the missing 80-odd days to 46 BCE (making it 445 days long), and then standardized the lengths of the months to what we know today: alternating 30 and 31 days, with pairs of 31s at the middle and end of the year, and a 28-day February with an extra leap day every fourth year to keep things on track.

Incidentally, he had nothing to do with renaming the months. That was all the Senate, and in fact happened after he died; Quintilis was renamed Iulius in that month 44 BCE, in honor of our boy's birthday, and Sextilis was renamed Augustus in 8 BCE because according to the Senate, many of the important events of Augustus's reign had occurred in that month.

(Then, 1600 years later, Pope Gregory XIII decided to account for the year being just a sliver shorter than 365.25 days, and we got the modern Gregorian calendar.)