I've been reading quite a lot about some countries in where, instead of a 5 working days week, they've implemented a 4 working days one. Apparently it benefits conciliation and people is more productive because of this working time. I'm not sure if it has to be regulated by the government or if it depends exclusively on the company. I'd like to try it on my own business, since it's a small one and I think it could work, but I don't know if I need any "permission" to do so. Any thoughts on this?

 I companies and busineses are opening and workers working 3-4 days because government mandated it so. 
I don't there is anything stopping companies from  adopting such working schedule if they see workers who can work with such and paid accordingly.