It is good to expose errors in history and in claims about alleged Catholic teaching. The idea that the Catholic Church changed the Sabbath from Saturday to Sunday is a myth. It is, however, true that worshipping God on Sunday and observing Sunday as a day of rest for free and slaves alike was promoted by the Catholic Church and the Church also promoted the freeing of slaves who were Christians. But these ideas originate in the gospels and the old testament so even though the Catholic Church promoted them they did not invent them.
Some claim that Sunday was first set aside for special treatment by emperor Constantine in the fourth century AD but this is clearly not true because first and second century Christians observed Sunday as special for the reasons given in my previous post. Saint Justin who was martyred by pagan Romans wrote these words about Christian worship in 150 AD, the middle of the second century, which is more than 150 years before Constantine's time as emperor:
Chapter LXVII.Weekly worship of the Christians.
And we afterwards continually remind each other of these things. And the wealthy among us help the needy; and we always keep together; and for all things wherewith we are supplied, we bless the Maker of all through His Son Jesus Christ, and through the Holy Ghost. 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. Then we all rise together and pray, and, as we before said, when our prayer is ended, bread and wine and water are brought, and the president in like manner offers prayers and thanksgivings, according to his ability, and the people assent, saying Amen; and there is a distribution to each, and a participation of that over which thanks have been given, and to those who are absent a portion is sent by the deacons. And they who are well to do, and willing, give what each thinks fit; and what is collected is deposited with the president, who succours the orphans and widows and those who, through sickness or any other cause, are in want, and those who are in bonds and the strangers sojourning among us, and in a word takes care of all who are in need. 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. For He was crucified on the day before that of Saturn (Saturday); and on the day after that of Saturn, which is the day of the Sun, having appeared to His apostles and disciples, He taught them these things, which we have submitted to you also for your consideration.
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click this link for the source at CCEL)