My favorite holiday that Romans celebrate (because I know everyone's clamoring to hear that) was probably The Secular Days
The use of "secular" here does not denote a lack of religion but rather comes from the Latin word saeculares which is a unit of time wherein every person alive at the start of one saeculum is dead by the start of the next one, Romans had a very cyclical view of time and a saeculum was the largest of those cycles. It ranged from 100-120 years and yeah they would have a huuuuge festival on the last day of one saeculum and the first day of the next one
The whole idea was that the festival was to be something no person alive had ever seen before or would ever see again. A very liminal time, transitioning from one massive cycle to the next. Tied into this, as it is into all of Roman life, was a litany of superstitions and religious ceremonies so it also took the shape of like,,,, rededicating the culture to its gods and performing sacrifices that also could only be done once a saeculum
Predictably, the whole thing was massive
That's just such a cool concept! It's my favorite holiday as it's probably the only one I know about that I'd actually be interested in doing lol
The last secular festival was held around 248 CE to denote Rome's supposed 1000th year, by the end of that saeculum the empire had Christianized to the point where the holiday was outlawed, and by the end of that saeculum the empire had collapsed. When they said "games the likes of which no man has seen nor will see again" they were unusually correct
