I have read in numerous commentaries on John 20 that Thomas first met the resurrected Christ on Sunday, the first day of the week. Here is one illustrative example, though others I've looked at are similar in substance:
Verses 26-31 We have here an account of another appearance of Christ to his disciples, after his resurrection, when Thomas was now with them. And concerning this we may observe,I. When it was that Christ repeated his visit to his disciples: After eight days, that day seven-night after he rose, which must therefore be, as that was, the first day of the week. Matthew Henry's commentary on John 20 [emphasis is mine]
Here are the relevant verses from the Bible:
John 20 (NKJV)
19 Then, the same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled, for fear of the Jews, Jesus came and stood in the midst, and said to them, “Peace be with you.” 24 Now Thomas, called the Twin, one of the twelve, was not with them when Jesus came. 25 The other disciples therefore said to him, “We have seen the Lord.” So he said to them, “Unless I see in His hands the print of the nails, and put my finger into the print of the nails, and put my hand into His side, I will not believe.” 26 And after eight days His disciples were again inside, and Thomas with them. Jesus came, the doors being shut, and stood in the midst, and said, “Peace to you!”
Perhaps I'm being naïve, but starting from the Lord's day, Sunday, I count "and after eight days" (Greek: "καὶ μεθ’ ἡμέρας ὀκτὼ") to mean the Monday of the following week, that is, eight days after the first Sunday. It seems that the commentaries I've read interpret it to mean "on the eight day", which would indeed work out to the following Sunday. However, I'm having difficulty understanding how "after eight days" can be understood in this way.
So, my question is: On what day of the week did Thomas first meet the resurrected Christ? Was it on a Sunday, a Monday, or some other day of the week?
My main interest in this question is to understand if these verses in John 20 are indeed a valid support for the practice of Christians meeting on Sunday. I don't question the practice (there are many other verses in Acts, 1 Corinthians and Revelation that support it); I am simply trying to understand whether John 20 indeed displays the first case of Christians meeting as Christians on two consecutive Sundays. I'm having a hard time seeing this in this particular chapter.