The only source that has told the world that the Bible is authentic and genuine is the Catholic Church. It compiled it, it preserved it and it has passed it out to the world. It is the keeper and the disseminator. The Sabbath Day was changed to Sunday under its authority. Because it has the authority. Christmas Day was decided upon because it had the authority to specify it. Ditto Easter. Ditto the Sacrament of Reconciliation (the forgiveness of sins). And so on.
Does the Bible matter to you and how much? If it doesn't, and your church is the standard, then we have nothing to discuss.
The Day after the sabbath (The Lords Day) is actually referenced in the Bible, you might try reading one.