dies solis (11. 407)

Though not the first sabbath observed as a day of rest, reflection and worship, on this day in 321 CE, Constantine the Great ordained that the Sun’s Day, styling himself as Sol Invictus, the Unconquered Sun, as the non-work day for urbanites of the Empire, with workshops closed and magistrates taking this venerable day off—though allowances were made for those in the agricultural sector, whose harvest and husbandry usually couldn’t stand on ceremony. Having declared tolerance for Christians a decade earlier with the Edict of Milan and later convoking the Council of Nicaea, Christianity adopted this Roman week-structure.