And we assemble together on Sunday, because it is the first day, on which God transformed darkness and matter, and made the world; and Jesus Christ our Savior rose from the dead on that day; for they crucified him the day before Saturday; and the day after Saturday, which is Sunday, he appeared to his apostles and disciples, and taught them these things which we have presented to you also for your consideration.
Exactly! There are some Christians who would like to move Christian worship away from Sundays in order to make the point that all days are alike. But something is lost in such a move. Sunday was "the Lord's Day" not for some random reason. It was "the first day" of creation in Genesis 1, the day on which God said, "Let there be light!" And it was the first day of the new creation—the day that Jesus was raised from the dead. Sunday holds together creation and new creation and Sunday worship is a fitting way of sanctifying time.