For those asking about how to get a four day work week - I've negotiated to a 4 day work week once, and do a 20 hour week a second time. Each time I just said it's what I wanted to do and the employer was on board, but each time was also after working full time for over a year. I'd try that route instead of looking for a new job that would do 4 days, as that seems pretty uncommon.