I have always wondered that the LDS do not observe the seventh day sabbath. Both the Bible and LDS scriptures affirm the holiness of the day, and its place in the 10 Commandments compels observance. Have you ever done a study of the subject?
Actually, the Seventh Day Sabbath was changed when Christ rose from the dead.
This is what I learned in Catholic school, and have never seen anything to dispute it. Sunday was changed to the day of worship for the Christians, to commemorate Jesus’ return to Earth. Of course, Easter is specifically the day, but Sundays are used to remind us.
I suspect somewhere along the line, it had to be a Papal edict, but until then, it became “official” by constant usage.
Muslims and Jews still use Friday at Sundown to mark the start of Sabbath.