Your passage is not evidence that they changed their Sabbath to the First day. They kept time differently than we do.
When the sun set, their day ended and their new day began. So, in Acts 20:7-9, they were likely gathered around on the Sabbath day already and when they broke bread on the First Day, it just means Saturday night. Paul began speaking in the evening and continued until sometime in the middle of the night.
Eutychus’ death gives evidence of what I say, because his falling asleep would indicate he’s tired at the end of the day rather than the beginning.
7 And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
8 And there were many lights in the upper chamber, where they were gathered together.
9 And there sat in a window a certain young man named Eutychus, being fallen into a deep sleep: and as Paul was long preaching, he sunk down with sleep, and fell down from the third loft, and was taken up dead.
——>Actually it was the early Christians, led by the apostles, long before the Roman Catholic Church began, that first began the Sunday Worship
Certainly not.
Did the Apostles Abandon The Sabbath
And Keep Sunday Instead
To Honor The Resurrection?
https://www.biblelightinfo.com/firstday.htm
Sunday is NOT the Sabbath!
https://www.biblelightinfo.com/notsun.htm
From Rome’s Challenge: (there is not one biblical word about keeping Sunday in place of the 7th-day-Sabbath)
https://www.romeschallenge.com/downloads/RomesChallenge.pdf
“The Protestants claim to stand upon the written word only. They profess to hold the Scripture alone as the standard of faith. They justify their revolt by the plea that the Church has apostatized from the written word and follows tradition. Now the Protestant’s claim, that they stand upon the written word only is not true. Their profession of holding the Scripture alone as the standard of faith, is false. PROOF: The written word explicitly enjoins the observance of the seventh day as the Sabbath. They do not observe the seventh day, but reject it. If they do truly hold the Scripture alone as their standard, they would be observing the seventh day as is enjoined in the scripture throughout. Yet they not only reject the observance of the Sabbath enjoined in the written word, but they have adopted and do practice the observance of Sunday, for which they have only the tradition of the Church. Consequently the claim of “Scripture alone as the standard.’ fails; and the doctrine of “Scripture and tradition” as essential, is fully established, the Protestants themselves being judges.”
https://www.biblelightinfo.com/firstday.htm
The Acts of the Apostles
Here in the second book attributed to Luke, written about 80 - 90 A.D., we now come to one of the most frequently quoted verses to support Sunday sacredness:
Acts 20:7 And upon the first day of the week, when the disciples came together to break bread, Paul preached unto them, ready to depart on the morrow; and continued his speech until midnight.
Clearly the disciples are meeting on Sunday, the first day of the week. It might even be presumed by some that by “breaking bread” they celebrated the Lord’s supper that Sunday. The question that needs to be asked though, is why were the disciples assembled on this day? What reason brought them together? In context, it will be seen that Paul was departing the next day on his journey to Jerusalem to be present during the Pentecost festival (v. 16). This gathering was a farewell assembly with Paul, the last day the people at Troas could meet with him, and that is why it lasted into the early morning hours. In fact Paul talked with them all through the night and then left in the morning at sunrise (v. 11).
Did Paul preach? Yes, without doubt, as verse 7 makes clear. Does that indicate the day was special, a holy day? No, they preached every day:
Acts 5:42 And daily in the temple, and in every house, they ceased not to teach and preach Jesus Christ.
Did they celebrate the Lord’s supper? Perhaps, yet even if they did, as some maintain, there is no indication that that Sunday, or any Sunday, was being observed as a newly instituted weekly holy day to commemorate the resurrection. The breaking of bread did not indicate a special day of worship, or even that the Lord’s supper was being celebrated, as scripture tells us they met daily and broke bread from house to house:
Acts 2:46 And they, continuing daily with one accord in the temple, and breaking bread from house to house, did eat their meat [food] with gladness and singleness of heart,
This indicates nothing more than eating what are called agape meals of fellowship, which are not necessarily connected with a formal worship service involving partaking in communion. Here is another example of breaking bread meaning a common meal:
Acts 27:33 And while the day was coming on, Paul besought them all to take meat [food], saying, This day is the fourteenth day that ye have tarried and continued fasting, having taken nothing.
Acts 27:34 Wherefore I pray you to take some meat [food]: for this is for your health: for there shall not an hair fall from the head of any of you.
Acts 27:35 And when he had thus spoken, he took bread, and gave thanks to God in presence of them all: and when he had broken it, he began to eat.
Now some will point to the celebration of Pentecost, found in Acts 2, and rightly claim that this occurred on a Sunday. Since that year the 16th of Nisan; the day of first fruits; which was a type of the resurrection; fell on Sunday, Pentecost would also fall on Sunday. However, those gathered in the upper room on that day were gathered because it was Pentecost, not because it was Sunday:
Acts 2:1 And when the day of Pentecost was fully come, they were all with one accord in one place.
Had they been gathered to observe the resurrection, wouldn’t Luke have told us that this was the new day of the week for all Christians to observe? But, you say, we do observe Pentecost always on a Sunday (Whitsunday). Perhaps you do, but not by anything directed in scripture. Pentecost, like Passover, is not tied to any particular week day. It is determined by the day of the month of the biblical lunar calendar, which means it does not always fall on Sunday. According to the scriptural calculation, Pentecost will most likely be on (or about) the 6th day of the third month, Sivan, which will only occasionally fall on the first day of the week. When the Catholic Church ruled in the Council of Nicaea in 325 A.D. that the resurrection (Easter) would always be observed on a Sunday (instead of the biblical 16 Nisan), this automatically resulted in Pentecost being observed only on a Sunday, but this change lacks any biblical support.
So, there is nothing in the book of Acts that leads us to believe that Sunday had been set aside as a weekly holy day of worship to honor the resurrection.