The next verse in Greek: [Acts 20:7] εν δε τη μια των σαββατων συνηγμενων των μαθητων του κλασαι αρτον ο παυλος διελεγετο αυτοις μελλων εξιεναι τη επαυριον παρετεινεν τε τον λογον μεχρι μεσονυκτιου
There is no Greek word for Sabbath, hence the translation from Hebrew speakers into Greek in this case is "Sabbatwn", the sixth Greek word in the above paragraph. Most English translations of [Acts 20:7] say something like this: 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. If you'll look at your Bibles you'll see that the word "day" is italicized....meaning that it is added.
The proper translation for this scripture is: And on the first of the Sabbaths...................... The first of the Sabbaths means just that...the first. What Paul is speaking of here is the first weekly Sabbath between Passover and Pentecost. The Jews numbered seven of them [Leviticus 23:15] and Paul, having just celebrated Passover (verse 6), is again meeting on the weekly Sabbath, also the first Sabbath in the count of the "Omer" to Pentecost. That's why the translation gives it a plural (Sabbatwn). It is both the weekly Sabbath and the first Sabbath between the two major Holydays which Paul and his companions obviously observe. We know this is the proper interval because in [Acts 20:16] Paul tells us he was in a hurry to reach Jerusalem by Pentecost.
In every Greek translation dealing with the resurrection you will find this word Sabbatwn....meaning a special Sabbath between Passover and Pentecost. If the meaning were the first day of the week, the Greek "hemera"(day) would be included. Here is the literal translation from [Matthew 28:1]. Same time period, different situation...actual resurrection. And on the eve of the sabbaths, at the dawn, toward the first of the sabbaths, came Mary the Magdalene, and the other Mary, to see the sepulchre. You can see the plurality of the word "Sabbatwn" meaning "Sabbaths". The eve of the Sabbaths means between the evenings, and you find that terminology in [Exodus 12:6] 'And it hath become a charge to you, until the fourteenth day of this month, and the whole assembly of the company of Israel have slaughtered it between the evenings....speaking of the Passover lamb.
I have no idea how people can be so ignorant of simple Biblical truth...and then when presented with it, just cast it off like so much garbage.....as I'm sure we'll hear soon.
Just an FYI, the SDA does not deny that people met on Sunday, or that at some point people decided to swap Sunday for the Sabbath. They teach that it was an error, but to deny it happened would be silly.