Every year I'm reminded of the time I learned about Roman calendars

[conuly]

And their batshit, batshit counting down system with inclusive counting.

The 15th is the Ides of March, and the day before that is pridie Ides March, okay - and then the day before that is "three days before the Ides". Because thirteen, fourteen, fifteen makes three days. And they used that every time they wanted to find a date, counted backwards (inclusively!) from the next Kalends, Nones, or Ides.

It broke my brain then and I've never fully recovered.

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Comments

[conuly]

I think that was fixed by the classical era, though it took Julius Caesar to fix their weird ad hoc system of having to announce the start of a new year.

[austin_dern]

Also the Leap Day was a doubling of what we'd call the 24th of February, or as they knew it, the sixth day to the kalends of March, which leads to the obscure term for a leap year as a ``bissextile year''.

Before they got to the regularly-scheduled-leap-day part of things, though, they'd sometimes just insert an extra month, Mercedonius, that would, according to some (contemporary) sources just slip in between the 23rd and 24th of February. (Other sources said February just ended even shorter than usual and Mercedonius took over until March.)

Anyway all this is why ancient Roman programmers almost never got their database calendars to work right.

[conuly]

I wonder if slipping in an extra month was a holdover from lunar calendar days. Isn't that why the Jewish calendar slips in extra months? If the month has to start at a certain stage of the lunar cycle you can't just add in days willy-nilly, it's got to be a whole month at a time.

[redbird]

I was surprised to learn that in the Hebrew calendar, leap years contain two Adars, but the extra month is inserted before the regular Adar, not after. I can't remember which bits of holiday and ritual this matters for, although Adrian explained it to me once.

[magid]

Hi! Reading my network page...

The holiday in the month of Adar is Purim, which is on the 15th of Adar, celebrating the story in the Book of Esther, which also happens to be tonight! :-)

There is debate among the Talmudic-era rabbis (200-400 CE ish, probably more on either side) whether Purim is in Adar I or Adar II, and even though most (all?) Jews celebrate in Adar II, the equivalent day in Adar I has some liturgical differences to show it's not a regular weekday.

Also, months always start with the new moon. Theoretically, an extra day could be added to a month if the next month's new moon wasn't sighted as soon as possible (the original Jewish calendar was not fixed, but relied on monthly testimony of witnesses attesting they've seen the new moon, and I believe there were signals sent out announcing the new moon using bonfires on hilltops). However, it wouldn't make up the difference between the lunar and solar calendar. Twelve months on the lunar calendar is about 354 days. Since the Jewish calendar requires Passover to be in the spring, an extra month was added when needed in Adar, the month before Passover, to ensure it stayed in the spring. This happens 7 times every 19 years. (If this didn't happen, Jewish holidays would move around the solar year, like Ramadan does.)

[conuly]

Aren't you supposed to get drunk on Purim? This comment sounds suspiciously not-drunk.

[magid]

There is a custom of getting drunk, but it's generally expected to happen at the Purim meal, which is a daytime commandment (ie today), not a nighttime one (although there are those always those up for alcohol :-), presumably to ensure that folks make it to both the night and morning/day readings of the Book of Esther, and being wildly drunk while listening is not considered ok.

However, the custom for drinking is to get the point of not knowing the difference between "Blessed is Mordechai" and "Cursed is Haman" (the main males of the story), which a significant subset of rabbis say can just as easily be fulfilled by.... taking a nap. I'm much more fond of naps than hangovers (plus it's a custom, not a requirement).

[conuly]

Well, go forth and nap, then!

[austin_dern]

Yes, by the way, the slipping in of an extra month was meant to keep what started as a lunar calendar roughly in synch with the solar.

Maybe useful context is the Roman calendar started out not covering the whole year, just, like, the start of spring to the end of harvesting. So it was a calendar in the way, like, the baseball season has a calendar, with days that just don't matter. The days-that-don't-matter provided the padding needed to keep time as best as possible in synch with sun and moon, but once you try putting a name and number to every day you start having to make compromises, some of them more preposterous than others.

There'll be a time in several thousand years, due to precession of the Earth's orbit, that either the Gregorian Calendar, the idea of Easter as an early-spring (European) holiday, or the tie between Easter and the first full moon in spring has to be given up. Likely at least one of these will have been given up before the choice is required, but even so, there's constraints that can't all be met indefinitely.