Sabbath is not just a day of the week. It is a state of worship/mind: A day set aside to worship God.
These days, some people have to observe their Sabbath on Wednesday.
Says who?
"Remember the Sabbath Day to keep it holy" is a directive to corporate worship with the rest of one's faith community. He didn't say, "Any day will do..."
We are of course to pray and be in communion with the Holy Spirit all day, every day. But the Commandment is about one Holy day set aside for one's blood family and faith family, and the Lord's Supper with those gathered—a day different from the rest.
That’s an easy, convenient cop-out. Defining your own “Sabbath” is like defining your own “gender.”