I live in Sweden and have never hard of any company doing a four day week. The closest I get is one of my first jobs which had a 37.5 hour week (rather than the customary 40 hours) but again, spread out over five days.
That said, some of the last few weeks at the time of writing have in practise turned out to be four day weeks due to public holidays. Could this be what causes the confusion?
I live in the Netherlands, here it depends completely on the "cao" that is used within the 'branche' (type of industry). There are industries that use 32, 36, or 40 hours as full-time work weeks. Most goverment jobs for example are either 36 or 32 hours.
I work in SWE, which is almost always 40 hours in my experience YMMV.
