Roman emperor Constantine the Great issues a new law establishing Sunday (dies Solis Invicti, or sun-day) as a day of rest.
Sunday had long been a Roman day for honoring the sun, but Christians had slowly been appropriating for themselves for their sabbath day.
Emperor Constantine's new law states:
"All judges and city people and the craftsmen shall rest upon the venerable day of the sun.
Country people, however, may freely attend to the cultivation of the fields, because it frequently happens that no other days are better adapted for planting the grain in the furrows or the vines in trenches.
So that the advantage given by heavenly providence may not for the occasion of a short time perish." [CI 3.12.2]