In 1908, a New England cotton mill instituted a 5-day workweek. The move inspired others to follow suit over the next 30 years until the Fair Labor Standards Act made 2-day weekends official in 1938. Now, over a century later, some tech companies are shaving another day off the workweek. Iceland’s national government trialed a 4-day workweek between 2015-2019, and found worker productivity either remained the same or improved. Even in Japan — where workaholism is so common there’s a word for overworking oneself to death, “kiroshi” — companies like Panasonic are letting employees opt in to the 4-day schedule. Should the extra day off be on Friday? Monday? Some other day? The only question left is when?