Strict 7-day weeks were a Jewish thing from sometime before 500 BC, unrelated to the Roman calendar. Even in other cultures that split time into weeks based on

Strict 7-day weeks were a Jewish thing from sometime before 500 BC, unrelated to the Roman calendar. Even in other cultures that split time into weeks based on lunar phases, weeks were adjusted to match the moon (a lunar week is ~7.4 days). From what I understand the Romans didn’t adopt a 7-day week as a core part of the calendar until after the emperor had converted to Christianity. See https://en.wikipedia.org/wiki/Nundinae https://en.wikipedia.org/wiki/Nundinae