If you run a search on the topic of the 4-day work week, you will discover thousands of articles referring to the seemingly successful 4-day work week trial program run by Microsoft Corporation in Japan last year.
By "4-day work week", we are specifically referring to fitting 5 days worth of work into 4 days and receiving the same amount of pay. This concept is based on the notion that employees waste time each day being unproductive at work and so, it is possible to for the same amount of work to be completed in four days, giving employees an additional day off and potentially boosting productivity.
This boost in productivity is exactly what Microsoft reported (40%) after its 1 month trial of a 4-day work week in Japan. The news story drew worldwide attention because of its attractive subject matter - suggesting a hopeful solution for the uphill battle for work-life balance.
As successful as the trial was branded to be in Japan, it is worth noting that there is no further report of working to permanently install the 4-day work week at that Microsoft location. And, in fact there are instances of companies reversing such previously installed policies (see: Harvard Business Review). This seems to imply that it is more of a complicated endeavor than it is publically advertised to be.