1 Corinthians 1
1 Corinthians 1:8 makes mention of "the day of the Lord" but it also points to the end times and the day of judgment. It speaks of the believers being confirmed in the end and "blameless in the day of our Lord Jesus Christ". No mention is made of weekly gatherings, the Sabbath, or a change to G-d's commandments.
1 Corinthians 5
1 Corinthians 5:5 also includes a reference to "the day of the Lord" and informs us that the incestuous member of the Corinthian assembly should be cast out and delivered to Satan for the destruction of his flesh so that his spirit may be saved in "the day of the Lord Jesus". Again we see Judgment Day in view here, not the Sunday the week after the expulsion of the reprobate member of the assembly. Once again... no mention is made of weekly gathering, the Sabbath, or a change in G-d's commandments in this passage.
2 Corinthians 1
2 Corinthians 1:13-14 makes mention of the day of the Lord. This passage again clearly refers to Judgment Day ("I hope you will understand until the end") rather than some weekly event. Following suit with the passages above no mention is made of weekly gathering, the Sabbath, or a change in G-d's commandments.
Philippians 1:6 tells us that "He who began a good work in you will perfect it until the day of Christ Jesus." Unless this passage teaches that a fresh batch of believers is perfected every Sunday we are again left with a reference to the end times and the time of Messiah's return.
Later in the chapter in Philippians 1:10 tells us that we should be "blameless until the day of Christ". If this passage teaches that the "day of Christ" is Sunday then we can find comfort that we only have to resist sin and temptation until the following Sunday and then we are perfect beyond that. The rest of us will likely be looking towards the end times and Christ's return for this particular event. The analysis: same song, different verse (pun intended): no weekly gathering, Sabbath, or changes to the commandments here.
2 Peter 3
2 Peter 3:10 tells us that on the "day of the Lord"
the heavens will pass with a roar and the elements will be destroyed with intense heat, and the earth and its works will be burned up.
For the seventh time we see that the "day of the Lord" refers to the end times. Just to be consistent: no weekly gathering, Sabbath, or changes to the commandments here.
2 Peter 3:12 also refers to the end times when the heavens will be destroyed by burning, and the elements will melt with intense heat. No weekly gathering, Sabbath, or changes to the commandments in that verse either.
In Revelation 1:10, John speaks of being in the Spirit on "the day of the Lord". Every other instance in Scripture mentioning "the day of the Lord" refers to Judgment Day and the end times. Is there anything in this passage to indicate that John is speaking of anything other than the end times? There is not.
Is there anything in this passage to indicate that John is speaking about the end times? John is delivering the book of Scripture whose substance is almost entirely devoted to the admonition of the seven churches of Asia and the revelation of the end times and the return of Messiah! Does this passage make any reference to the weekly gathering of believers, the Sabbath, or a change to G-d's holy seventh day? It does not.
Summary of part 2
These nine passages are the only mentions made in the apostolic writings regarding "the day of the Lord" and variations on that phrase. None of them make any mention of a specific day of the week, the Sabbath, the gathering of believers, and none of them provide any indication that the Sabbath day was changed.
In part 3 of this series we will examine some additional references to determine if there are any changes to G-d's holy Sabbath day in the New Covenant.