The Sabbath was established at creation, it is the seventh day of the week. If you need further proof look up saturday in a dictionary and you will find out that saturday is indeed the seventh day of the week. For your information Emperor Constantine decreed on 7 March 321 that sunday would now be the official day of rest in the kingdom as it was the day Jesus rose from the tomb, authority he did not have, God never changed the Sabbath.
The Sabbath was given to Israel, not the church. The Sabbath is still Saturday, not Sunday, and has never been changed. But the Sabbath is part of the Old Testament Law, and Christians are free from the bondage of the Law (Galatians 4:1-26; Romans 6:14). Sabbath keeping is not required of the Christian-be it Saturday or Sunday. The first day of the week, Sunday, the Lord's Day (Revelation 1:10) celebrates the New Creation, with Christ as our resurrected Head. We are not obligated to follow the Mosaic Sabbath-resting, but are now free to follow the risen Christ-serving. The Apostle Paul said that each individual Christian should decide whether to observe a Sabbath rest, "One man considers one day more sacred than another; another man considers every day alike. Each one should be fully convinced in his own mind" (Romans 14:5). We are to worship God every day, not just on Saturday or Sunday. Read more: http://www.gotquestions.org/Saturday-Sunday.html#ixzz2MEYdYo4o ;