I'm confused. Rome didn't have a 7 day week until Constantine introduced it in 321 CE Rome used an 8 day cycle called "nundinal cycle". (And yes the name of t

I'm confused. Rome didn't have a 7 day week until Constantine introduced it in 321 CE Rome used an 8 day cycle called "nundinal cycle". (And yes the name of the 8 day cycle contains the root of the number 9, novem, because Romans of course also invented off-by-one errors) Days were named with letters from A to H. What does it mean that the Panis Quadratus was baked on a Wednesday? That sparked my curiosity and I tried to find more accounts of this alleged ritual of baking specific kinds of breads on specific days of the week but I couldn't find much. It seems that somebody wrote a piece about panem quadratus on Wednesday and a few other types of breads and that's got copy-pasted around including some touristic website from Naples. I call bullshit, but I may be wrong. Does anybody know more about it?