The texts used to support the belief that God's Sabbath was changed from the 7th day to the 1st day of the week (John 20:19, Acts 20:6-11, and 1 Cor 16:1-3) cannot stand up to the truth that God never changed the day. Here in Acts 13, it is clear that the disciples continued to worship on the 7th day Sabbath. They did not change God's day of worship to Sunday to celebrate Christ's resurrection. I think it's fair to say they celebrated it by proclaiming the gospel to the ends of the world.
The Catholic Church has stated on more than one occasion that she changed the day to Sunday under the authority that she believes God has given her to replace Him here on earth. A huge part of the reason for the change came at a time when the church wanted to gain control; as such, the pagan day to worship the sun was embraced, within a melding of church and pagan traditions. This way everyone could be happy--or so they thought.
And let me just say that the whole notion of the Mark of the Beast dividing the masses today is an inaccurate notion. The Mark of the Beast and the Seal of God do not come into play until persons must make a decision to follow God or follow the world. That won't happen until the Sunday worship laws are being enforced. This will be the period of time foreshadowed by Stephen's sermon and subsequent stoning, the last chance to get it right before your decision seals your fate for eternity.