Forgive me for jumping in Buggman.....but I cannot pass this up!
How about Matthew 28:1, in the original Greek, [Now late on Sabbath as it was getting dusk toward first of week came Mary the Magdalene and the other Mary to see the sepulchre]. Verse 6 says, [He is not here for He has risen as He said. Come see the place where was lying the Lord]. notice the past tense.
The above is the only definitive place in scripture that says when he arose from the tomb.....and it was on the Sabbath, late in the afternoon.
The tradition of most of organized Christianity today ignores this and continues their Sunday celebrations.
Oh, if only someone would ask me that :)
Before I answer, let me pose YOU a question: Do you really think that wether you worship on Sunday or Saturday is a serious concern? I think that having a "day of rest" dedicated to the Lord is more important rather than the day. The tradition you trying to use as an example is a poor one to argue.