Appreciate your reply - I believe I read somewhere that Constatine (early century) changed the Sabbath from Saturday to Sunday when he broke away from the Roman Church. Although I have not read the entire Bible - I don't recall reading in the New Testament that the day had been changed.
The sabbath was changed in honor of the day the Lord rose.
Constantine never broke away from the church - he was a very strong convert to it. He wasn't even baptized until an hour before his death. He did that in order to ensure his salvation. Would that we could all believe that strongly.
Your source is definitely wrong. Firstly, there was no "change" of the Sabbath, since Sunday is not kept by Catholics as a sabbath day, as if nothing had changed except the date.
Early Christian sources such as St. Justin Martyr (~150 AD) and the Letter of Pseudo-Barnabas (~70-130 AD) indicate that Sunday was already being kept and that the Sabbath was not.
And on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read, as long as time permits; then, when the reader has ceased, the president verbally instructs, and exhorts to the imitation of these good things ... But Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead. (Justin Martyr, First Apology, § 67)
And when they ceased, I again addressed them thus:-"Is there any other matter, my friends, in which we are blamed, than this, that we live not after the law, and are not circumcised in the flesh as your forefathers were, and do not observe sabbaths as you do? Are our lives and customs also slandered among you? And I ask this: have you also believed concerning us, that we eat men; and that after the feast, having extinguished the lights, we engage in promiscuous concubinage? Or do you condemn us in this alone, that we adhere to such tenets, and believe in an opinion, untrue, as you think?" ...
And when no one responded: "Wherefore, Trypho, I will proclaim to you, and to those who wish to become proselytes, the divine message which I heard from that man. Do you see that the elements are not idle, and keep no Sabbaths? Remain as you were born. For if there was no need of circumcision before Abraham, or of the observance of Sabbaths, of feasts and sacrifices, before Moses; no more need is there of them now, after that, according to the will of God, Jesus Christ the Son of God has been born without sin, of a virgin sprung from the stock of Abraham. ... (Justin Martyr, Dialogue with Trypho the Jew, §§ 10, 23)
Further, He says to them, “Your new moons and your Sabbath I cannot endure.” [Isa. i. 13.] Ye perceive how He speaks: Your present Sabbaths are not acceptable to Me, but that is which I have made, [namely this,] when, giving rest to all things, I shall make a beginning of the eighth day, that is, a beginning of another world. Wherefore, also, we keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead. And when He had manifested Himself, He ascended into the heavens. (Letter of Barnabas)
The Lord's Day (Sunday) is referred to in Rev. 1:10.
Constantine lived early 4th Century. Ignatius of Antioch (early second century) is already congratulating his flock for "no longer Sabbathing" but for observing the commemoration of the Lord's resurrection on Sunday. Justin Martyr (mid second century) says the same thing, in describing the Christian liturgy being celebrated "on the first day of the week, the day named for the sun". Christian Sunday worship long preceded Constantine. In fact, even one of the more learned Seventh Day Adventist scholars now admits that Sunday celebration existed in apostolic times.