What does the book of Acts mean when it says.......

"But 

Q: what did the writer of the Acts of the Apostles mean by the word “Sabbath,” and the “Sabbath day”?
A: Acts 13:44 The next Sabbath day came almost the whole city together to hear the word of God. He does not say this was the

Jewish sabbath, but the Sabbath day; this was the seventh day; and the first day of the week was not then known as a Sabbath by this writer; because he says the next Sabbath day the Jews and Gentiles most all came together again. 

I say there would not have been any next Sabbath in the week till the next seventh day. 

Again, Acts 16:13 And on the Sabbath we went out of the city by a river side, where prayer was wont to be made. He does not say on the Jewish, nor on one of the sabbaths, as though there were two sabbaths then, but on the Sabbath, i.e. the seventh day, as understood by all the Jewish writers, to this day." 

Elihu