Not true. The Companion Bible answers: The fact that "three days" is used by Hebrew idiom for any part of three days and three nights is not disputed; because that was the common way of reckoning, just as it was when used of years...but, when the number of nights is stated as well as the number of days, then the expression ceases to be an idiom, and becomes a literal statement of fact. (1990, appendix 144).
Regarding Matthew 28:1; The American Standard version says: [Now late on Sabbath day].....The Bible basic English says: [Now late on the Sabbath].....The Darby Bible says: [Now late on Sabbath].....The Webster's Bible Translation says: [In the end of the Sabbath].....and the King James Version says: [In the end of the Sabbath]. They all say in verse 6....[He is not here; He has risen].
The reason most people cannot accept simple Bible truth is that it destroys the theology they have been taught since childhood. When you learn the "Good Friday/Sunday resurrection story" is a fairy tail it makes you feel betrayed.
Why do you suppose the Apostles prohibited a Thursday fast and required a Friday one if Jesus were crucified on Thursday instead of Friday?
Diego, based on what you write, am I correct in assuming you are affiliated with a Sabbatarian group in Southern California known as the "Church of God"?