This study is designed to demonstrate reorganization of the social and religious time in the later Roman empire through legislation of Christian feasts by the Theodosian Code. It first examines the social rhythm of Roman society in the middle of the 4th century with recourse to the Codex-Calendar of 354. Then it proceeds to demonstrate how the imperial laws in the fourth and fifth centuries had changed traditional Roman time into Christian time. The legislation of Sundays/Lord’s days as feriae publicae introduced weekly holidays into Roman society. Subsequent laws designated Christian feasts such as Easter, Epiphany, and Christmas as public holidays, while they abolished feriae connected with pagan gods, thereby making them workdays. Creation of many imperial anniversaries may be understood as a process of modifying a pagan Roman society into a Christian one. Reorganization of the social time can also be seen in imperial legislation which prohibited spectacles on Christian feast days. Many imperial laws which abrogated pagan cults and superstitions and strove to preserve and keep spectacles demonstrate secularization of public entertainment. Furthurmore, prohibition of spectacles, even those linked to imperial anniversaries, on Christian feast days as well as conceptual distinction between “time for prayer” and “time for entertainment” displays a process of separation between religion and festivals. Other imperial laws emphasized humanitarian concerns on Christian feasts. They demanded Easter amnesty, prohibition of tortures during Lenten seasons, and visitation of prisoners on every Sunday. This study corroborates that the process of Christianization of the later Roman empire included reorganization of the social and religious time through imperial legislation.