Four-Day Work Week
Last summer we experimented with 4-day work weeks. People should enjoy the weather in the summer. We found that just about the same amount of work gets done in four days vs. five days.
So if that’s the case we could either push everyone to work harder during those five days or we could just skip one of those days. We decided to skip one of those days.
Jason Fried, 37signals' Workplace Experiments