The resurrection was on Sunday. That's why so many Christian Churches gather on that day. And they were gathering on that day, and as well as others, long before Constantine's decree.
There is no requirement in the New Testament to keep the 4th commandment and its Saturday sabbath. Everyone is free to choose their day and Sunday as the day of Resurrection and Pentecost is quite appropriate.
Can you give me a scripture eliminating the Sabbath command? It is very interesting to see how quickly you have mended fences with the apostolics. My Bible reads from Genesis to Revelation, the faith is to the same God throughout, the same God who sanctified the 7th Day in Genesis is the same God I worship.