Catholics do not observe the Sabbath. The Sabbath is the seventh day of the week (Saturday) and is observed by Jews and by some Christian groups who have rejected the Catholic understanding that Christians no longer observe the Sabbath (e.g., Seventh-Day Adventists).
From the earliest times, Catholics have observed Sunday as the Lord's Day, which is "expressly distinguished" from the Jewish Sabbath (CCC 2175
). Sabbath was the memorial of creation and God's rest on the seventh day; Sunday commemorates the new creation instituted by Christ's Resurrection on the first day of the week. While early Christians celebrated both Sabbath and Sunday -- mainly because the early Church included a significant number of Jews who had converted to Christianity -- as the Church became predominantly Gentile, the observance of the Sabbath by Christians eventually ceased.
While the Sabbath included a number of laws restricting what one could do on that day -- the reason for which was to promote active rest, not legalism -- the Church's regulations for Sunday were mainly concerned with insisting that Catholics go to Mass and have the time free from work to do so (which is why legislation arose in Christian countries closing businesses on Sunday). The Church generally has not concerned itself with making other restrictions on what people may do on Sunday. While avoiding servile work is encouraged by the Church, and while the Church promotes Sunday rest, it is left to individual Catholics to determine what genuinely constitutes meeting the obligation to "refrain from engaging in work or activities that hinder the worship owed to God, the joy proper to the Lord's Day, the performance of the works of mercy, and the appropriate relaxation of mind and body" (CCC 2185
Sabbath or Sunday?
From Sabbath to Sunday
by James P. Guzek
by John Paul II