The 7th Day was NOT observed for centuries.
Thou shalt observe the Sabbath, on account of Him who ceased from His work of creation, but ceased not from His work of providence: it is a rest for meditation of the law, not for idleness of the hands." "The Anti-Nicene Fathers," Vol 7,p. 413. From "Constitutions of the Holy Apostles," a document of the 3rd and 4th Centuries.
"When you are in Rome, do as Rome does." —Ambrose, the celebrated bishop of Milan gave rise to this proverb by stating that when he was in Milan he observed Saturday, but when in Rome he observed Sunday.
"The ancient Christians were very careful in the observance of Saturday, or the seventh day...It is plain that all the Oriental churches, and the greatest part of the world, observed the Sabbath as a festival...Athanasius likewise tells us that they held religious assembles on the Sabbath, not because they were infected with Judaism, but to worship Jesus, the Lord of the Sabbath, Epiphanius says the same." "Antiquities of the Christian Church," Vol.II Book XX, chap. 3, sec.1, 66. 1137,1138.
"In the last half of that century (4th) St. Ambrose of Milan stated officially that the Abyssinian bishop, Museus, had 'traveled almost everywhere in the country of the Seres' (China). For more than seventeen centuries the Abyssinian Church continued to sanctify Saturday as the holy day of the fourth commandment." Ambrose, DeMoribus, Brachmanorium Opera Ominia, 1132, found in Migne, Patrologia Latima, Vol.17, pp.1131,1132.
Canon 26 of the Council of Elvira (3005ad) reveals that the Church of Spain at that time kept Saturday, the seventh day. "As to fasting every Sabbath: Resolved, that the error be corrected of fasting every Sabbath." This resolution of the council is in direct opposition to the policy the church at Rome had inaugurated, that of commanding Sabbath as a fast day in order to humiliate it and make it repugnant to the people.
Persia-A.D. 335-375
"They despise our sun-god. Did not Zorcaster, the sainted founder of our divine beliefs, institute Sunday one thousand years ago in honour of the sun and supplant the Sabbath of the Old Testament. Yet these Christians have divine services on Saturday." O'Leary, "The Syriac Church and Fathers," pp.83, 84.
Council Laodicea - A.D.365
"Canon 16-On Saturday the Gospels and other portions of the Scripture shall be read aloud." "Canon 29-Christians shall not Judaize and be idle on Saturday, but shall work on that day; but the Lord's day they shall especially honor, and as being Christians, shall, if possible, do no work on that day." Hefele's "Councils," Vol. 2, b. 6.
Let me jump a few centuries to save time and space...
Scotland and Ireland 7th century
Professor James C. Moffatt, D.D., Professor of Church History at Princeton, says: It seems to have been customary in the Celtic churches of early times, in Ireland as well as Scotland, to keep Saturday, the Jewish Sabbath, as a day of rest from labour. They obeyed the fourth commandment literally upon the seventh day of week." "The Church in Scotland," p.140.
Scotland 10th century
"They worked on Sunday, but kept Saturday in a Sabbatical manner." A history of Scotland from the Roman Occupation, Vol. I, p.96. Andrew Lang
Church Of The East - Kurdistan
"The Nestorians eat no pork and keep the Sabbath. They believe in neither auricular confession nor purgatory." Schaff-Herzog, "The New Encyclopaedia of Religious Knowledge," art. "Nestorians."
Waldenses
"And because they observed no other day of rest but the Sabbath days, they called them Insabathas, as much as to say, as they observed no Sabbath." Luther's "Fore-Runners" (original spelling), PP. 7, 8
Roman Catholic writers try to evade the apostolic origin of the Waldenses, so as to make it appear that the Roman is the only apostolic church, and that all others are later novelties. And for this reason they try to make out that the Waldenses originated with Peter Waldo of the twelfth century. Dr. Peter Allix says:
"Some Protestants, on this occasion, have fallen into the snare that was set for them...It is absolutely false, that these churches were ever found by Peter Waldo...it is a pure forgery." Ancient Church of Piedmont, pp.192, Oxford: 1821
"It is not true, that Waldo gave this name to the inhabitants of the valleys: they were called Waldenses, or Vaudes, before his time, from the valleys in which they dwelt." "Id., p. 182
On the other hand, he "was called Valdus, or Waldo, because he received his religious notions from the inhabitants of the valleys." History of the Christian Church, William Jones, Vol II, p.2
I could go on, every century having evidence of Sabbath observance. And every century having evidence of the Catholic church's hatred for the Sabbath, and her determination to get rid of it, and persecute Sabbath observers. Just as Christians on this forum attempt to do every time it comes up in discussion.