The FIRST day. “LET THERE BE LIGHT”
Where on earth do we get our light? The SUN. Yes, the same Sun as in SUNday. So.. First day is Sunday.
No harm in worship on all days.
Exactly right. I know you recall that they tried to convict Christ for not following the Sabbath and the same bunch eventually murdered him. Christ IS the new Sabbath. If you got 4 or 5 minutes, this video lays that out pretty well in a short period of time.