The Catholic Church claims responsibility for the change from seventh-day to first-day Sabbath. Here is an explanation from The Catechism of the Catholic Church Section 2 Article 3 (1994):
Sunday – fulfillment of the Sabbath. Sunday is expressly distinguished from the Sabbath which it follows chronologically every week; for Christians its ceremonial observance replaces that of the Sabbath...
The Sabbath, which represented the completion of the first creation, has been replaced by Sunday which recalls the new creation, has been replaced by Sunday which recalls the new creation inaugurated by the Resurrection of Christ...
In respecting religious liberty and the common good of all, Christians should seek recognition of Sundays and the Church’s holy days as legal holidays.
And here are various Catholic sources claiming the change was the doing of the Roman Catholic Church:
Cardinal James Gibbons, The Faith of Our Fathers (Ayers Publishing, 1978): 108:
But you may read the Bible from Genesis to Revelation, and you will not find a single line authorizing the sanctification of Sunday. The Scriptures enforce the religious observance of Saturday, a day which we never sanctify.
The Convert's Catechism of Catholic Doctrine (1957): 50:
Q. Which is the Sabbath day?
A. Saturday is the Sabbath day.
Q. Why Do we observe Sunday instead of Saturday?
A. We observe Sunday instead of Saturday because the Catholic Church transferred the solemnity from Saturday to Sunday.
Chancellor Albert Smith for Cardinal of Baltimore Archdiocese, letter dated February 10, 1920:
If Protestants would follow the Bible, they should worship God on the Sabbath day by God is Saturday. In keeping the Sunday, they are following a law of the Catholic Church.