(Maybe this should be saved for the Friday PC question of the day):
A Day is based on the rotation of the earth
A Month is based on the orbit of the moon
A Year* is based on the orbit of the earth around the sun.
While the Torah defines the construct of a Week - is there any celestial cycle underpinning the concept of a week? IOW - aside from the torah laying out the week of creation and defining shabbos, is there any reason to explain the concept of a week?
Whilst not really answering your question, it is mentioned in Jewish texts about 7 מזלות which each are dominant for an hour and every 7 hours they restart from #1.
That leads to מזל מאדים always being dominant on Fridays between 6-7 (and between 11am and 12 on Friday and between 1-2am on Saturday)
I don't know if these מזלות are connected to anything physical.