John, that is pure fiction, pure fantasy, pure lies. The early church Fathers wrote about how and why Sunday became the day of assembly for group worship more than a hundred years before that. Below are statements from early church writings.
You should actually see when it was legitimized...
Constantine, Catholicism, sun worship and the Sabbath to Sunday change
In 312 A.D., prior to his pivotal victory over his rival Maxentius at the Battle of Milvian Bridge, Constantine became a “Christian” after claiming to see in broad daylight a vision of “a cross above the sun” with these words emblazoned, “in hoc signo vinces” (by this sign conquer”). After defeating his enemies and becoming Emperor of Rome, Constantine presided in full royal pomp over the “First Council of Nicea” in 325 A.D.
A shrewd political genius, his scheme was to unite paganism and Christianity in an effort to strengthen his disintegrating empire. Constantine knew that pagans throughout the empire worshiped the sun on “the first day of the week,” and he discovered that many Christians and especially in Rome and Alexandria also kept ‘Sunday’ because Christ rose from the dead on that day. So Constantine developed a plan to unite both groups on the common platform of Sunday keeping. On March 7, 321 A.D., he passed his famous national Sunday law:
“On the venerable Day of the Sun let the magistrates and people residing in cities rest, and let all workshops be closed.” Source: Codex Justinianus, lib. 3, tit. 12, 3; trans. in Philip Schaff, History of the Christian Church, Vol.3 (5th ed.; New York: Scribner, 1902), p.380, note 1.
Now if you believe that these guys had the "Primacy of Peter" and could overrule scripture, then by all means do what you think is right (reminds me of a Proverb). The problem is the Catholic church itself takes the credit for changing the day of worship to Sunday...
“Is not every Christian obliged to sanctify Sunday and to abstain on that day from unnecessary servile work? Is not the observance of this law among the most prominent of our sacred duties?
But you may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify.” James Cardinal Gibbons, The Faith of Our Fathers (1917 edition), p. 72-73 (16th Edition, p 111; 88th Edition, p. 89).
“For example, nowhere in the Bible do we find that Christ or the Apostles ordered that the Sabbath be changed from Saturday to Sunday. We have the commandment of God given to Moses to keep holy the Sabbath day, that is the 7th day of the week, Saturday.
Today most Christians keep Sunday because it has been revealed to us by the [Roman Catholic] church outside the Bible.” Catholic Virginian, October 3, 1947, p. 9, article “To Tell You the Truth.”
“Question: How prove you that the church had power to command feasts and holydays?
“Answer: By the very act of changing the Sabbath into Sunday, which Protestants allow of and therefore they fondly contradict themselves by keeping Sunday strictly, and breaking most other feasts commanded by the same church.
“Question: Have you any other way of proving that the church has power to institute festivals of precept?
“Answer: Had she not such power, she could not a done that in which all modern religionists agree with her; -she could not have substituted the observance of Sunday the first day of the week, for the observance of Saturday the seventh day of the week, a change for which there is no Scriptural authority.” Stephen Keenan, A Doctrinal Catechism On the Obedience Due to the Church, 3rd edition, Chapter 2, p. 174 (Imprimatur, John Cardinal McCloskey, Archbishop of New York).
“Perhaps the boldest thing, the most revolutionary change the Church ever did, happened in the first century. The holy day, the Sabbath, was changed from Saturday to Sunday. ‘The day of the Lord’ was chosen, not from any direction noted in the Scriptures, but from the (Catholic) Church’s sense of its own power...People who think that the Scriptures should be the sole authority, should logically become 7th Day Adventists, and keep Saturday holy.” St. Catherine Church Sentinel, Algonac, Michigan, May 21, 1995.
“Nowhere in the Bible is it stated that worship should be changed from Saturday to Sunday...Now the Church...instituted, by God’s authority, Sunday as the day of worship. This same Church, by the same divine authority, taught the doctrine of Purgatory long before the Bible was made. We have, therefore, the same authority for Purgatory as we have for Sunday.” Martin J. Scott, Things Catholics Are Asked About, 1927 edition, p. 136.
“Question - Which is the Sabbath day?
“Answer - Saturday is the Sabbath day.
“Question - Why do we observe Sunday instead of Saturday?
“Answer - We observe Sunday instead of Saturday because the Catholic Church, in the Council of Laodicea (A.D. 364), transferred the solemnity from Saturday to Sunday.” Peter Geiermann, C.S.S.R., The Convert’s Catechism of Catholic Doctrine, p. 50, 3rd edition, 1957.
“They [the Protestants] deem it their duty to keep the Sunday holy. Why? Because the Catholic Church tells them to do so. They have no other reason...The observance of Sunday thus comes to be an ecclesiastical law entirely distinct from the divine law of Sabbath observance...The author of the Sunday law...is the Catholic Church.” Ecclesiastical Review, February 1914.
“The Sunday...is purely a creation of the Catholic Church.”American Catholic Quarterly Review, January 1883.
“Sunday...is the law of the Catholic Church alone...” American Sentinel (Catholic), June 1893.
“Sunday is a Catholic institution and its claim to observance can be defended only on Catholic principles...From beginning to end of Scripture there is not a single passage that warrants the transfer of weekly public worship from the last day of the week to the first.” Catholic Press, Sydney, Australia, August 1900.
“It is well to remind the Presbyterians, Baptists, Methodists, and all other Christians, that the Bible does not support them anywhere in their observance of Sunday. Sunday is an institution of the Roman Catholic Church, and those who observe the day observe a commandment of the Catholic Church.” Priest Brady, in an address reported in The News, Elizabeth, New Jersey, March 18, 1903.
All according to what your authority is, the Bible or the Catholic church.
My comments in blue.
Oh yeah and let's see here, who lied?