Sabbath or Sunday one truth one tradition

The Sabbath VS Sunday has been a long standing issues amongest Christians down through the centuries, resulting in many passionate debate and labeling those that hold to the Sabbath as legalistic, therefore not worthy of consideration.Since one of these two is truth and the other nothing more than a tradition of man's own invention, is would seem reasonable, possible and to ones best interest to determine which is truth and the other tradition. For one is told by Christ that in vain do you worship me, teaching for doctrines the commandments of men. For laying aside the commandments of God, you hold the tradition of men. Full well you reject the commandment of God, that you may keep your own tradition. So it is extremely beneficial for one that hold the teachings of Christ to insure that they do not worship him in vain, by holding the tradition of men. For the point of his declaration was not that one thinks or feels like they are not worshipping him in vain, for those he was speaking to did not think or feel they were unsuccessful in their reverence to God, but he was enlightening them to that undeniable truth. I have been on both side of this issue so I am some what familar with each sides arguments also I have written a book on the subjest.Before I present my evidece to show which of the two is truth and the other tradition, I would like to here from you concerning which one is truth and your defense for it. Here are a few questions for your consideration: Could something start out being a truth of God and later become a tradition of men? It said God blessed the seventh day which mean he spoke favorably of it and he was its defender, so show from the gospels accounts of the life of Christ were he was a champion for the honour of Sabbath? Then for the first day of the week Sunday? God promised his rest to man so give evidecne of its fulfillment so it can be changed or does it remain?