Officially MCMICIX. But in actual Roman times, you’d see IMM or MIM, albeit unofficially after numbers were standardized. Well, you would if they needed that number.
Of course, earlier versions had no subtraction at all, so you’d get MDCCCCLXXXXVIIII. Or you would if they used M–I don’t think it existed yet.
Also used a lot in crossword puzzles, presumably when they need they need a filler to make the other words fit. Like “Ulee” or “Ione”.
As to the OP, I learned it in elementary school but it was in one of those “advanced” classes where we also learned color names like “puce” and “vermillion” and had to make construction paper models of dodecahedrons (sp.).In other words, I don’t think it was widely taught; just to us kids that got to learn the weird and useless stuff (not that I’m complaining).
Often the clue will be something like “Year in the reign of Claudius” but sometimes a lazy editor will do no more than provide “4th century date”.
Last year’s Superbowl was called Superbowl 50 by the NFL, they claim for aesthetic reasons, but this year they will once again do as the Romans do and the big game will be Superbowl LI. Of course that is sooooo much more pleasing to the eye than Superbowl L.
The Superbowl thing doesn’t really do much for the *stereotype *that football fans are a bunch of beer guzzling dumb asses(please note, I said stereotype). As if the NFL are overly concerned about aesthetics?:dubious: