There are eight texts in the New Testament that mention the first day of the week. Look at them carefully.

Matthew 28:1

After the Sabbath, as the first day of the week was dawning, Mary Magdalene and the other Mary went to view the tomb.

Mark 16:1&2

When the Sabbath was over, Mary Magdalene, Mary the mother of James, and Salome bought spices, so they could go and anoint Him.

Very early in the morning, on the first day of the week, they went to the tomb at sunrise.

Mark 16:9

Early on the first day of the week, after He had risen, He appeared first to Mary Magdalene, out of whom He had driven seven demons.

Luke 24:1

On the first day of the week, very early in the morning, they came to the tomb, bringing the spices they had prepared.

John 20:1

On the first day of the week Mary Magdalene came to the tomb early, while it was still dark. She saw that the stone had been removed from the tomb.

John 20:19

In the evening of that first day of the week, the disciples were gathered together with the doors locked because of their fear of the Jews. Then Jesus came, stood among them, and said to them, “Peace to you!”

Acts 20:7 & 8

On the first day of the week, we assembled to break bread. Paul spoke to them, and since he was about to depart the next day, he extended his message until midnight.

There were many lamps in the room upstairs where we were assembled.

1 Corinthians 16:1 & 2

Now about the collection for the saints: You should do the same as I instructed the Galatian churches.

On the first day of the week, each of you is to set something aside and save in keeping with how he prospers, so that no collections will need to be made when I come.

The first five texts simply state that the women came to the sepulcher early on the resurrection morning, and that Jesus rose from the dead.

Now let’s take another look at John 20:19

In the evening of that first day of the week, the disciples were gathered together with the doors locked because of their fear of the Jews. Then Jesus came, stood among them, and said to them, “Peace to you!”

It tells us that Jesus appeared to the disciples later on the resurrection day. It says that the reason they were assembled was for “for fear of the Jews.” They were scared.

No telling when the Jews might grab them and treat them to the same fate as their Master. They were hiding. They had seen their beloved Master die on Friday.

Luke 23:56

Then they returned and prepared spices and perfumes. And they rested on the Sabbath according to the commandment.

And now they’re hiding with the doors shut “because of their fear of the Jews”  as per John 20:19

There’s no mention of a change.

The seventh text is Acts 20:7 & 8. It says:

On the first day of the week, we assembled to break bread. Paul spoke to them, and since he was about to depart the next day, he extended his message until midnight.

There were many lamps in the room upstairs where we were assembled.

The dark part comes first. The Bible reckons a day from sunset to sunset. The seventh day begins at sunset Friday evening. The first day begins sunset Saturday evening. Paul is together with his friends on the dark part of the first day of the week-Saturday night.

This is a farewell get together. He preached until midnight, when poor Eutychus falls out of the window.

Acts 20:9

And a young man named Eutychus was sitting on a window sill and sank into a deep sleep as Paul kept on speaking. When he was overcome by sleep, he fell down from the third story and was picked up dead.

You can imagine how relieved they were when it was found that God spared his life.

Verse eleven says that they talked till the break of day and then Paul departed.

Verse thirteen shows that Paul spent Sunday morning traveling to Assos.

There’s nothing here either concerning a change of the Sabbath.

The New English Bible translates Acts 20:7 like this:
On the first day of the week, when we met to break bread, Paul began to speak to the people, and because he intended to leave the next day, he extended his message until midnight.

The last text mentions the first day of the week in 1 Corinthians 16:1 & 2. It says:

Now about the collection for the saints: You should do the same as I instructed the Galatian churches.

On the first day of the week, each of you is to set something aside and save in keeping with how he prospers, so that no collections will need to be made when I come.

Verse three tells that he will bring the offering to Jerusalem. As he had done in Galatia, so Paul also requests of those in Corinth to have a collection all ready when he would come to take it to the poor saints in Jerusalem.

There’s nothing in the text about a church service, but each person is to “lay by him in store.” The first day of the week was the best time for the people to set some money aside because later in the week it would be spent. That’s true today as well!

Paul requested this so that “no collections will need to be made when I come.” 1 Corinthians 16:2