The 7th day Saturday Sabbath was the Sabbath day up until the cross. But once Jesus died and then rose again early Sunday morning God made a change in Sabbaths. He ended the Old Testament Saturday Sabbath and began the New Testament Sunday Sabbath day. The Greek word for Sabbath is sabbatōn (σαββάτων). Sabbaton is a plural word which should be translated as "Sabbaths". In Matthew 28:1, Sabbaton is found twice. Once it’s mistranslated in the singular as "Sabbath" and once its mistranslated as "week". In both places it should be translated in the plural as "Sabbaths.” Here's the verse:

Matthew 28:1 In the end of the sabbath, as it began to dawn toward the first day of the week,...

Now let's correct the translation:

Matthew 28:1 In the end of the Sabbaths, as it began to dawn toward the first of the Sabbaths,...

In order for us to understand this verse we have to keep in mind that this statement is being made early Sunday morning. Saturday has ended and Sunday is beginning. For thousands of years Saturday (7th) identified with the Old Testament Sabbath day. But now, as Jesus rose from the dead early Sunday morning, God declares it to be the END OF THE SABBATHS! That is, the end of the O.T. 7th day Sabbath has come to pass. Further, the Lord immediately institutes a new Sabbath day for the N.T. era. It is to be the resurrection day of Christ, "as it began to dawn toward the first of the SABBATHS.” The change has been made. Sunday is now the Sabbath. And once God makes a change in program like this, if anyone says 'not so' and continues to insist on doing it the old way (i.e. worshiping God on the 7th day)--they are in outright rebellion against God and come under the wrath of God.

‍