"The sanctification of the Lord’s day (or the first day of the week) is also implied in Revelation 1:10 where the Apostle John says, “I was in the Spirit on the Lord’s day.” John speaks of a day which is distinct from all other days. “Some say, how do we know that this was the first day of the week? Every day is the Lord’s day. But it is the design of John to tell us when he had those visions. And if by the Lord’s day is meant any day, how doth that inform us when that event took place?” [39] John uses an expression that Christians in his day would instantly recognize as the day of Christ’s resurrection: the first day of the week. Seventh-day Adventists argue that this refers to the Saturday, Jewish sabbath. But this assertion is clearly unscriptural. “Nowhere in God’s Word is the Saturday sabbath ever called the ‘Lord’s day.’... The adjective in the expression—‘kuriake (-os, -on)’ [i.e., the Lord’s]—occurs in only one other verse of scripture: in 1 Cor. 11:20 in the expression ‘the Lord’s Supper’ (‘kuriakon deipnon’), which supper was usually held on the first day of the week. This very fact surely implies that the Lord’s day (‘he kuriake hemera’) was also then held on the first day of the week.” [40] A passage of Scripture which clearly identifies the Lord’s day as the day of Christ’s resurrection is Psalm 118:22-24: “The stone which the builders rejected has become the chief cornerstone. This was the LORD’s doing; it is marvelous in our eyes. This is the day the LORD has made; we will rejoice and be glad in it.”
The Apostle Peter, in addressing the Sanhedrin (Ac. 4:8-12), applies Psalm 118:22 directly to the exaltation of Jesus Christ, which began at His resurrection (cf. Mt. 28:18, Rom. 4:3-4). [41] Psalm 118 identifies the day of Christ’s exaltation as a day of rejoicing and gladness. Were the disciples of Jesus rejoicing on the seventh day (Saturday)? Were they glad and happy on that day? No, absolutely not. On Saturday Jesus was dead and still laid up in a tomb. On Saturday the disciples were in mourning. Their leader had been put to death as a common criminal. They were living in fear, doubt, sorrow and apparent defeat; but on Sunday, the first day of the week, Christ rose from the dead; and their tears turned to joy, their sorrow to gladness, their doubt to hope, and their defeat to victory. “This is the day the Lord has made; we will rejoice and be glad in it” (Ps. 118:24). This is the origin of the term “the Lord’s day.” It is the day on which the Christian church celebrates the victory of the Son of David. “We observe the Lord’s day as henceforth our true Sabbath, a day made and ordained of God, for the perpetual remembrance of the achievements of our Redeemer.... Entering into the midst of the church of God, and beholding the Lord Jesus as all in all in the assemblies of his people, we are bound to overflow with joy. Is it not written, ‘then were the disciples glad when they saw the Lord’?” [42]
The historical evidence presented thus far is sufficient to prove that Jesus Christ has changed the sabbath day from the seventh to the first day of the week. Jesus rose from the dead on the first day of the week. He appeared to His disciples on the first day on more than one occasion. The disciples gathered together on resurrection Sunday, and then again at Pentecost, in order to meet with the risen Christ. The apostolic church engaged in public worship on the first day of the week. [43] This involved preaching, the sacraments and tithing. The Apostle Paul indicated that first-day public worship was universal in the churches of Galatia. The Apostle John used the phrase “the Lord’s day” as a time reference that all the churches of Asia Minor would instantly recognize: the day of Christ’s resurrection (Ps. 118:22-24), the day of joy and worship. “Must we not conclude that these inspired men regarded the authority of God as now attaching to this Lord’s day?” [44] Yes, we must."
That's a very nice explantion of tradition, but where in scripture does it say that the 7th day of the week is no longer the sabbath and the 1st day of the week is?
Matthew 28:1, [Now late on Sabbath as it was getting dusk toward first of week came Mary the Magdalene and the other Mary to see the sepulchre.]
Verse 6, [He is not here for he has risen as he said. Come see the place where was lying the Lord.]
This is the original Greek in the Textus Receptus(Received Text)
As you can see by the scripture he arose before sundown on the Sabbath Day. Many translations say something similar like "at the end of the Sabbath" or "Now late on Sabbath" as the Greek says. Other translations, because of theological bias, say something like "After the Sabbath was over" or some other variation.....but the original Greek shows that our Lord was resurrected on the Saturday Sabbath.