During the first and second century the week of seven days was introduced into Rome from Egypt, and the Roman names of the planets were given to each successive day.
St. Ignatius (Ep. ad Magnes. ix) speaks of CHRITIANS as "no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also Our Life rose again". 
These and similar indications show that during the first three centuries practice and tradition had consecrated the Sunday to the public worship of GOD by the hearing of the Mass and the resting from work. With the opening of the fourth century positive legislation, both ecclesiastical and civil, began to make these duties more definite. The Council of Elvira (300) decreed: "If anyone in the city neglects to come to church for three Sundays, let him be EXCOMMUNICATED for a short time so that he may be corrected" (xxi)
St. Cæsarius of Arles in the sixth century teaching that the holy Doctors of the Church had decreed that the whole glory of the Jewish Sabbath had been transferred to the Sunday, and that CHRISTIANS must keep the Sunday holy in the same way as the Jews had been commanded to keep holy the Sabbath Day.
The method of reckoning the Sunday from sunset to sunset continued in some places down to the seventeenth century, but in general since the MIDDLE AGES the reckoning from midnight to midnight has been followed.
A Council of Laodicea, held toward the end of the fourth century, was content to prescribe that on the Lord's Day the faithful were to abstain from work as far as possible. At the beginning of the sixth century St. Caesarius, as we have seen, and others showed an inclination to apply the law of the Jewish Sabbath to the observance of the CHRISTIAN SUNDAY. The Council held at Orleans in 538 reprobated this tendency as Jewish and non-Christian.