There may be a grain of truth there, but you are really stretching it. We worship on Sunday because Christ rose from the dead on that day. Christians began meeting on Sundays long before Constantine.
Agree and yet also disagree.
Then why do Orthodox Jews and Seventh Day Adventists (I think) consider the Sabbath day to be Saturday? Is that not the actual 7th day of the week? Last time I checked God rested on the seventh day, not the first (Sunday). Are these traditions not fairly long withstanding in and of themselves?
Granted I will give you that distinction is arbitrary, as we could arrange our calendar differently or recite the days of the week with different terminal points so long as we kept the same order.
On top of that, yes we observe the crucifixition and subsequent resurrection on a Friday/Sunday, but do we really have any proof that it happened on a Friday/Sunday? Why not a Monday/Wednesday? Is it any less amazing or meaningful that way?
Edit: actually we do, but the point still stands that it's no less meaningful. Sorry I'm tired after work and class. My bad, but I'll leave my mistake in here and own up to it.
It reminds me slightly of people who swear that Jesus Christ was on born December 25, 0000. If you dare suggest it could have been any time during the census, you are a heretic.
I quite frankly think that it's the spirit of the thing that matters here and not the actual mechanics of it. I dare say the dates/days of the week we choose have to do with convenience and tradition (as fistful points out, obliquely) than any sort of true historical accuracy.