I know some people hold this view, and some say that the Catholic church itself teaches this. I don't care if the devil himself teaches it. Remember that the Catholic church teaches that it is really one and the same as the church of Peter and the apostles of the lamb, something I dispute. The question is: if they did change it, when did they change it? The Catholic church teaches that they have MAINTAINED and PRESERVED the oral traditions of the apostles and the early church, so I doubt they changed this one in the 4th century. That would not fit. People say it was done in the time of Constantine. I don't believe this, because the Scriptures themselves give every indication that the believers celebrated the Lord's resurrection weekly on the first day of the week, what we call Sunday. Acts 20:7 and 1 Cor. 16:9 refer to the first day of the week and that is the best evidence we have from the New Testament.

If someone wants to set Saturday aside to worship God, let them do so, but once they start trying to push it on us all as a requirement for righteousness, they have misunderstood the true nature of Sabbath and have fallen into legalism.

If something like this was so vital for salvation and righteousness as some people claim, then there is no way that Paul would have written what he did in Colossians 2:16,17

"So let no one judge you in food or drink, or regarding a festival or a new moon or sabbaths, which are a shadow of things to come, but the substance is of Christ." (Colossians 2:16,17).

Frequently there are movements to spice up our Christianity by injecting some Jewish traditions and laws but these movements are dangerous today for the same reason that they were dangerous in the time of the apostle Paul, who wrote a lot about these things in his epistles, especially in the Book of Galatians.