Everywhere in the world we deal with a similar calender, consisting of 12 months and roughly 52 weeks of 7 days. Also universally around the world saturday and sunday are referred to as "the weekend", regardless of wether that entails days off or not.
In most of the west, we now have the convention of the 7 day week being divided in 5 work days and 2 days off work. Due to the increase in production per person (by better manufacturing methods) some argue that it's time to go to the 4 day work week, giving folks 3 days a week off. On the production side of the spectrum employers claim this would be too drastic a drop in work hours.
So why not move to 5 workdays and 3 days off?
As a unit of time, a year is based on our revolution around the sun. A month is (roughly) based on the lunar cycle. A day is based on the revolution of our planet around its own axis. The week is based on... nothing. It is a complete human fabrication.
Aside from the logistical issues of a worldwide adaptation, what do you think about the concept of this 8 day week?