Two points

1) I read years ago that many different weeks were used, and the 7 day week was of middle-eastern origin. Other weeks varied from 4 to 10 days.

2) Isaac Asimov proposed a system of 4 quarters, each of 91 days, plus a 'year day', each year. The week was still 7 days, but each quarter started on the same day of the week, and the 'year day' didn't count as any day of the week.

Sounds very boring to me.