sabbath

Most Christians believe that Sunday is a special day of worship and rest, every week commemorating the Resurrection of Jesus on the first day of the week on the Jewish calendar. Most Christian traditions teach that there is an analogy between the obligation of the Christian day of worship and the Sabbath-day ordinance, but that they are not literally identical—for a believer in Christ the Sabbath ordinance has not so much been removed as superseded, because God's very work of creation has been superseded by a "new creation" (2 Corinthians 5:17), according to this Christian view.
For this reason, most teach that the obligation to keep the Sabbath is not the same for Christians as in Judaism, and for support they point to examples in the New Testament, and other writings surviving from the first few centuries. Some conservative Christians, most of them within the Reformed tradition, are "Sabbatarians," believing the first day of the week or Lord's Day to be the new covenant Sabbath (the 4th commandment never having been revoked and Sabbath-keeping being in any case a creation ordinance).
Still others believe that the Sabbath remains as a day of rest on Saturday, reserving Sunday as a day of worship. In reference to Acts 20:7, the disciples came together on the first day of the week (Sunday) to break bread and to hear the preaching of the apostle Paul. This is not the first occurrence of Christians assembling on a Sunday; Jesus appeared to the Christians on the "first day of the week" while they were in hiding.
One can maintain this argument in that Jesus himself maintained the Sabbath, although not within the restrictions that were mandated by Jewish traditions; the Pharisees often tried Jesus by asking him if certain tasks were acceptable according to the Law (see: Luke 14:5). This would seem to indicate that while the Sabbath was still of importance to the Jews, Sunday was a separate day for worship and teaching from Scriptures.