ACTS 20:7
On the first day of the week when we gathered to break bread (COMMUNION), Paul spoke to them because he was going to leave on the next day, and he kept on speaking until midnight.
The 7th days is still the Sabbath.
Sunday has always been the Lord's Day.Almost everyone of Paul's letters tell us the old covenant has passed away and been broken for those that believe in CHrist, we must follow Christ and his new covenant, celebrated on his day. Read early Christian writings long long before Constatnine such as Justin Martyr, Tertullian, Ireneaus, Hipothylus they all talk of Christians celelbrating on the Lord's Day since the second century. Long before this link you are trying to make.
Assemble on the Lord's Day, and break bread and offer the Eucharist; but first make confession of your faults, so that your sacrifice may be a pure one. [The Didache 14:1 written 60 CE]
And we too rejoice in celebrating the eighth day; because that was when Jesus rose from the dead... [Epistle of Barnabas written 100 CE]
We have seen how former adherents of the ancient customs have since attained to a new hope; so that they have given up keeping the Sabbath, and now order their lives by the Lord's Day instead - the Day when life first dawned for us, thanks to Him (Jesus) and His death. [St. Ignatius of Antioch Epistle to the Magnesians written 110 CE]
And the Council of Laodicea was 336 not 337