Christians have observed a first-day (sometimes "eighth-day") Sabbath since the second century AD. https://en.wikipedia.org/wiki/Sabbath_in_Christianity#Early_...
1) reasons http://www.vatican.va/archive/ccc_css/archive/catechism/p3s2...
Actually, I'm not very good speaking english. It's not my first language, if anything, it's the last one. :P