Sunday is the Lord’s Day not the Shabbat.  The Christian principle of the Commandment is that we take the time to worship God but not necessarily as a literal Mosaic/Jewish observance.  The Orthodox, Catholic and Protestant tradition of Christianity maintains the Kurioke Hemera.  It’s not intended as a replicated Sabbath.   The Early Church worshiped on both days.  Saturday in Synagogue.  Sunday in Christian gatherings to commemorate Christ and the Resurrection.   The Jews ejected the Christians and Christians didn’t force themselves back in.  Hence where we are now. Edits: clarified language.