Yes, it was corrected previously. The Sabbath day is the seventh day (Saturday for you) while the first/eighth day is the traditional day of worship for (the vast majority of) Christians beginning after the Resurrection and continuing until now.
That is right, a tradition. Not following that tradition and observing Sabbath was a source of persecution throughout the history of the Church. I make the hypothesis that tradition kept the Jew separate while dispersed among the nations.