"On the first day of the week, when we were gathered together to break bread, Paul talked with them, intending to depart on the morrow; and he prolonged his speech until midnight" (Acts 20.7 RSV). St. John Chrysostom cited Acts 20.7 as a testimony.
"Therefore let no one pass judgment on you in questions of food and drink or with regard to a festival or a new moon or a sabbath." (Col. 2.16 RSV). "These are a shadow of the things that were to come; the reality, however, is found in Christ" (Col. 2.17 NIV).
"And we too rejoice in celebrating the eighth day; because that was when Jesus rose from the dead..." (Epistle of Barnabas 15).
"We have seen how former adherents of the ancient customs have since attained to a new hope; so that they have given up keeping the Sabbath, and now order their lives by the Lord's Day instead - the Day when life first dawned for us, thanks to Him (Jesus) and His death" (Epistle to the Magnesians 9).
Hebrews 4.8 speaks of "another day" (today) because the former Sabbath as not obeyed. "For if Joshua had given them rest, he would not have spoken afterward of another day." (Heb. 4.8 ASV).
Rev. 1.10, St. John "was in the Spirit on the Lord's day" (KJV).
The Holy Spirit descended upon the Church on Pentecost Sunday (Acts 2.1ff).
Resurrection of Christ occurred on Easter Sunday (John 20.1ff). "Now on the first day of the week Mary Mag'dalene came to the tomb early, while it was still dark, and saw that the stone had been taken away from the tomb" (John 20.1 RSV).
After His resurrection, Jesus appeared to the Apostles twice, each on Sunday (John 20.19,26): "On the evening of that day, the first day of the week, the doors being shut where the disciples were, for fear of the Jews, Jesus came and stood among them and said to them, 'Peace be with you...And after eight days again his disciples were within, and Thomas with them: then came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you'."
Jesus and the disciples were harassed by the Pharisees over the Sabbath (John 5.18): "This was why the Jews sought all the more to kill him, because he not only broke the sabbath but also called God his Father, making himself equal with God."
Jesus spoke out against the Pharisee's merciless observance of the Sabbath (Matt 12.1-8; Luke 13.10-16).
Jesus also defended Himself and His disciples on this issue by saying: "The sabbath was made for man, not man for the sabbath" (Mark 2.27 RSV).
"Now concerning the contribution for the saints: as I directed the churches of Galatia, so you also are to do. On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that contributions need not be made when I come" (1 Cor. 16.1-2 RSV).
Gather together weekly though there is no required appointed time or day, http://www.bible.ca/7-sunday-1st-day.htm