The seven-day week doesn't line up with the sun or the moon, and that was the point
A rest day with no astronomical justification turned out to be one of the most durable ideas in religious history.
Every other ancient calendar tracked something in the sky. Months followed the moon. Years followed the sun. The seven-day week followed nothing, no eclipse, no solstice, no visible event ties neatly to a seven-day cycle. Which is exactly why scholars find it so strange that it stuck.
The Hebrew Bible ties the Sabbath to the story of creation: six days of work, then a seventh set apart, sanctified, and commanded rather than merely suggested. Whatever its deeper prehistory (some scholars trace threads back to Babylonian lunar observances that eventually detached from the moon entirely), what emerged in ancient Israel was something genuinely new: a holy day that repeated on a schedule the sky itself doesn't keep.
The nineteenth-century Jewish thinker Ahad Ha'am put the payoff in a line that's outlasted most of his other writing: more than the Jews kept the Sabbath, the Sabbath kept the Jews. A single recurring day of rest, unmoored from nature, became one of the load-bearing walls of an entire people's continuity, and the ancestor of the Christian Sunday and the Muslim Friday that followed it.
Sometimes the most stabilizing thing you can build is something the world outside gives you no reason to expect.