The real, biblical Sabbath is sunset Friday to sunset Saturday, which is observed by observant Jews to this day. The early Christians celebrated and rested on Sunday, the Lord’s day, on which he rose from the dead.
I was a missionary in the Arabian Gulf and our weekend there was Thursday-Friday, so we had church on Friday. As Christians we have flexibility because we have died to the Law and now live according to our relationship with our Father!
As I said in answer to a question about tattoos:
Read Genesis 17:9-14, and note how absolute it is.
Now read Galatians and see Paul’s response to people who saw that and thought that Christians needed to be circumcised. We have died to the Law, and have been adopted as God’s beloved children! The paradigm has changed from obedience to the Law, to our relationship with our Father and loving our neighbors.
A rest day is good for us, but the particular day of the week is not an issue - so if someone (a pastor, for example, or an ER doctor) has to work on weekends but has another day off, that’s perfectly fine.