Acts 13:14-15
But when they departed from Perga, they came to Antioch in Pisidia, and went into the synagogue on the Sabbath day and sat down. And after the reading of the Law and the Prophets, the rulers of the synagogue sent to them, saying, “Men and brethren, if you have any word of exhortation for the people, say on.”
Acts 13:42-44
So when the Jews went out of the synagogue, the Gentiles begged that these words might be preached to them the next Sabbath. Now when the congregation had broken up, many of the Jews and devout proselytes followed Paul and Barnabas, who, speaking to them, persuaded them to continue in the grace of God. On the next Sabbath almost the whole city came together to hear the word of God.
Acts 16:13
And on the Sabbath day we went out of the city to the riverside, where prayer was customarily made; and we sat down and spoke to the women who met there.
Acts 17:2
Then Paul, as his custom was, went in to them, and for three Sabbaths reasoned with them from the Scriptures,
Acts 18:4
And he reasoned in the synagogue every Sabbath, and persuaded both Jews and Greeks.
It seems like a major change happened in the 2nd century AD to persuade Christians to gather on Sundays instead of the Sabbath.