I wasn't saying anything about any "incorrect day" but rather after Christ's resurrection, early believers chose to worship the Lord on the first day, the day He was resurrected, rather than the seventh day.
As The Lord himself, said, the "Sabbath was made for mankind, not mankind for the Sabbath."
What is sin? How can we know if we have sinned? Is it by "feelings"? My emotions may betray me. I see a rich man with plenty and I have little, my intellect may tell me it's okay to steal. How can I know it is wrong unless there is a law that clearly states what is permissible and what is not? The first four Commandments (not suggestions) tell me my duty to God. The last six is my duty to man. Satan whispers that these Commandments mean nothing. You decide for you, I'll go by the manual.