Yes, but the (supposed) instructions from God don’t actually say that the Sabbath must be arrived at by an unbroken count from an original Creative week, just that one day in seven be sanctified in numerological imitation. As I tried to explain once before,
Genesis 2:2-3; Exodus 16:23-30, 20:11, 23:12, 31:13-17, and 35:2-3; Leviticus 23:3; etc., refer to a “seventh day,” a day following six work days, sanctified and observed as such. I don’t see a specification for a particular day.
Yes, I understand that the Jewish Sabbath is traditionally Saturday, or rather that Saturday is the day in the traditional Jewish count that they called Shabbat as their designated Sabbath .
But that’s just a tradition, one possible proper observance. Because of the sundown-to-stars demarcation, it’s not even the same time frame for members of the same tradition in different places.
Beyond that, I understand in the Mishnah Rav Huna says that if a man is wandering in the wilderness and does not know which day it is in the common or traditional count, he should simply count off six days and then observe the next as a Sabbath. (A dissent says he should observe one day as Sabbath, then count off six.) He “recognizes his Sabbath” by the kiddush and havdalah rituals. It is the reverence and act of observance which signifies his obedience to God, not the time frame per se.
So why would it matter if some group faithfully observed, and made traditional, another day? It seems to me it shouldn’t be theologically significant if some community kept their Sabbath on Tuesday, as long as they rested, did no servile work, kindled no fire, and so on.
That’s all it is, a traditional schedule. Bookkeeping, you might say. There are seven possible six-and-one schedules that conform to the Biblical mandate. One has very long standing among Jews, another merely very long standing among most Christians. The others were perhaps used sometimes by wanderers in the wilderness, or isolated communities, or round-the-world travelers who paid attention to sunsets.