I had a company that allowed half day Fridays if we worked 9 hours a day M-Thu. I only chose to do that once. Staying in the office twiddling your thumbs for an extra hour felt more excruciating for me.

I would prefer we adapt a flex schedule type of work. If you’re done for the day you should be able to leave instead of acting like you’re busy.

Why though? As I pointed out in my other comment — based on actual historical data — productivity went UP when people switched to a 40 hour workweek. We need to get passed this idea that the literal number of hours are somehow sacrosanct. When we switched to a 40 hour workweek, productivity went up for a whole host of reasons, not least because of health and safety. It’s a marathon, not a sprint, and people aren’t literal cogs despite the Taylorism still prevalent in so much of our thinking around “work”.

Do you mean working less than 40 hours per week is counterproductive?

No, not at all. I’m pointing out that people fought against limiting the workweek to 40 hours but productivity ended up rising. Point being: fewer hours doesn’t mean productivity will necessarily go down. So if we’re gonna go to a four day week, why make the days longer?

I'm from the Netherlands and its an option that's quite common for companies that have 36 hour work weeks; 1) take Friday afternoon off (or Wednesday if you're children are off from school) 2) have a full day off once every other week, 3) have an extra day off every week but work 9 hours the other four.

Personally 9 hours per day wouldn't work, after a solid day of programming I tend to loose focus too much after about 7 hours, but some of the alternatives work fine.

Ye 9 hour days are pretty brutal - my optimal would be a 7 hour day, even for a slight reduction in salary

AFAIK the optimal is known to be 5 hours. I can't recall the sources but I believe this is backed with some recent neuroscience or empirical productivity experiments.