Geiermann, a Catholic writer, says that the Church changed the day in the 4th century at the Council of Laodicea.

You have misunderstood him. The Church then merely gave a special pre* cept ordering the faithful to keep to the Apostolic practice of observing Sunday, But the change was not made in the 4th century for the first time. Thus St. Augustine wrote in the 4th century, “The Apostles and their contemporaries sanctioned the dedication of Sunday to the worship of God.” Two centuries before Augustine, Tertullian had written, “We, as tradition has taught us, observe the day of the Lord’s resurrection.” St. Justin Martyr, who died in 167 A.D., wrote, “On Sunday we meet to celebrate the Lord’s Supper and read the Gospels and Sacred Scripture, the first day on which God changed darkness, and made the world, and on which Christ rose from the dead.” Earlier still, St. Ignatius, who died in 107 A.D., says, “If we still live according to the Jewish observances, we confess that we do not accept the grace of Christ. Those who once lived according to the Old Law have come to a new hope, no longer observing the Jewish Sabbath, but the Lord’s day on which our Life rose from the dead.” Thus tradition goes back to the indications given in Scripture and recorded above. Yet it is right to say that the Catholic Church changed the day in so far as the Apostles were representatives of that Church; for they, with the authority of Christ, sanctioned the change.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty