Show from the Bible that God established Saturday as the Seventh Day of the week. Scripture always speaks of “the seventh day”, never of a named weekday. Israel’s week is numeric: day one, day two, … day seven. The names “Saturday,” “Sunday,” etc., come from Roman planetary naming, not the Bible. There is nothing holy about the Roman Calendar.
It is the 7th day. And it does not matter what it is called in man's culture or language. The 7th day is the 7th day.
As far as proving which day is the sabbath.
Look at the life of Jesus. He would not have gotten the day wrong. Jesus obeyed the law perfectly.
Mat 28:1 In the end of the sabbath, as it began to dawn toward the first day of the week, came Mary Magdalene and the other Mary to see the sepulchre.
In German language the day for mid week is Wednesday.. which makes sabbath, saturday, the 7th day.
Luk 23:56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment.
AI states.... The Sabbath is traditionally defined in the Bible as the seventh day of the week, which corresponds to Saturday, lasting from Friday sunset to Saturday sunset. God rested on the seventh day after creation, making it a holy day of rest. While many Christian denominations now observe Sunday as the day of worship to mark Jesus' resurrection, others continue to recognize Saturday as the Sabbath.
In over 100 languages, the word for Saturday is derived from "Sabbath" or its Hebrew equivalent, Shabbat. This linguistic connection highlights that the seventh day of the week, commonly known as Saturday, is widely understood to be the Sabbath day in many cultures and languages.
There is no debate about which day of the week is the seventh day of creation.
The seventh day of creation is Saturday and this is the day that God blessed and sanctified.
Keeping the sabbath.... = sunset Friday until sunset Saturday.
The Jews have not lost track of time..