Okay, I get it. It sounds as if you believe in a literal seven (24-hour) day creation, and mankind's ability to have maintained a perfect record of each 7-day week since God took a "day of rest" after completing the Creation. See, to me, neither of those concepts make much sense. I do not believe in a young earth, a 7-day creation or perfect record keeping since "the beginning." I believe that God wants us to observe a day of rest once a week, to set aside that day as one where we worship Him and try to refocus on the blessings He's given us. I don't believe that He is so petty as to care whether we do that on a Friday, a Saturday or a Sunday, as long as we do it. Mormons are definitely committed to keeping the Sabbath Day holy, but we do observe it on Sunday, in commemoration of the day Jesus Christ rose from the dead.
As far as the Bible is concerned, we use the King James Version. It is one of four volumes of scripture we believe the Lord has given us for our edification and spiritual growth. Since we believe a general Apostasy took place shortly after the deaths of Christ's Apostles, we do not see the Roman Catholic Church as ever having held the authority Jesus Christ gave to Peter to lead the Church once He'd ascended to Heaven. It was, however, the Catholic Church who safeguarded the writings that now constitute the Christian Bible. While the Bible is definitely imperfect, it is most certainly far better than nothing. Any time human hands are involved in compiling, preserving, transcribing or translating an ancient text, there are going to be flaws in it. But without the Catholic Church, we would have no Bible at all today, so Mormons acknowledge the fact that they did give us what we now have, regardless of whether it is complete or inerrant..
I think God made himself plain. He said he created earth in 6 days and rested on the 7th, not the 3rd, or 4th of 1st day of the next week. It was to be a sign between him and His people. The sign between the dragon and his people is keeping the 8th day, the 1st day of the next week holy, such as when the lake of fire receives its sacrificial offering. "Christ" didn't rise on Sunday. On the eve of the 1st day of the week, he was already gone, 3 days and nights after he was buried, which was just before the eve of the high sabbath of the feast of Unleavened Bread (15th of Nissan), which was began on a Wednesday evening of the 14th day of Nissan/Passover. The day starts on the eve of the previous day. The "end of the Sabbath" is in the evening of the 7th day, not the morning of the following day. You have been duped.
King James Bible Matthew 28:1
In the end of the sabbath, as it began to dawn toward the first day of the week, came Mary Magdalene and the other Mary to see the sepulcher.