If you are doing this for only part of the year, one thing to be aware of is the Hawthorne Effect [0]. We're wired to seek novelty, and you may see a temporary increase in productivity each time you change working hours because of this. It's actually a reasonable argument for changing things around periodically, as long as it doesn't happen too often. (Note, however, that the effect may be limited to actual experiments where you're making careful observations. There isn't good consensus on it.)

[0] https://en.wikipedia.org/wiki/Hawthorne_effect

I love that you're doing this!

If you are interested in sharing some of your experiences doing this, email me at [email protected]

People love reading about this kind of stuff and I would be happy to feature your company on the site/newsletter. If you're hiring, past featured companies have received some quality candidates from this!

Best of luck in your experiment! Please consider writing up your thoughts afterwards, and perhaps sharing them with HN.

If you can really make up for the lost time through increases efficiency, would you consider keeping the four day week all year round?

Years ago, when I lived in Boston, when Summer arrived, half of the city went on water or did something outdoors. When I moved to CA, there was no such pattern as there is "Summer" the whole year around.

I'm wondering how different would your approach be if you are based in this kind of climate. For instance, we give our employees 30 days of PTO. If they wanted, they could easily use 8 days to take day off each week during Summer (or any other period), but we have not run into any that would do that.

This is definitely an area that I would like to explore more in the future. Thank you for sharing your experiences!

1) It's fantastic you've done this. This sort of thing would make me crazy about my employer.

2) "We certainly haven’t made up for the lost day in measurable improvements or efficiencies"

Maybe that's OK? Humans have tons of stuff already (at least in the rich world), and most of the things that are expensive are going to stay that way because we create false scarcities to soak up any extra income (housing, mostly).

I suppose that's why we need controls to level the playing field, or else the company willing to push workers for another day will lower the bar for everyone.

I think you're on the right track, best of luck with it!

I am quite sure I would get at least as much -- and probably more -- done if my week were formally four days long instead of five. I'm also sure this could be true, depending on motivation, of everyone I work with and almost everyone I ever have worked with.

This deserves to be its own hackernews post/writeup, and would easily make the front page!

French?

The comment mentions London. Not impossible by train, only unlikely :)

Parisians often go to London for weekends

"summer in London"

Parisians often go to London for weekends