“Seven days,” wrote Witold Rybczynski in the August 1991 issue of The Atlantic, “is not natural because no natural phenomenon occurs every seven days.” The year marks one revolution of the Earth around the sun. Months, supposedly, mark the time between full moons. The seven-day week, however, is completely man-made. If it’s man-made, can’t man unmake it? For all the talk of how freeing it’d be to shave a day or two off the five-day workweek, little attention has been paid to where the weekly calendar came from. Understanding the sometimes arbitrary origins of the modern workweek might inform the movement to shorten it. The roots of the seven-day week can be traced back about 4,000 years, to Babylon. The Babylonians believed there were seven planets in the solar system, and the number seven held such power to them that they planned their days around it. Their seven-day, planetary week spread to Egypt, Greece, and eventually to Rome, where it turns out the Jewish people had their own version of a seven-day week. (The reason for this is unclear, but some have speculated that the Jews adopted this after their exile in Babylon in the sixth century B.C.) At the very latest, the seven-day week was firmly entrenched in the Western calendar about 250 years before Christ was born. The earliest recorded use of the word “weekend,” Rybczynski notes, occurred in 1879 in an English magazine called Notes and Queries: In Staffordshire, if a person leaves home at the end of his week’s work on the Saturday afternoon to spend the evening of Saturday and the following Sunday with friends at a distance, he is said to be spending his week-end at So-and-so. Some 19th-century Britons used the week’s seventh day for merriment rather than for the rest prescribed by scripture. They would drink, gamble, and enjoy themselves so much that the phenomenon of “Saint Monday,” in which workers would skip work to recover from Sunday’s gallivanting, emerged. English factory owners later compromised with workers by giving them a half-day on Saturday in exchange for guaranteed attendance at work on Monday. It took decades for Saturday to change from a half-day to a full day’s rest. In 1908, a New England mill became the first American factory to institute the five-day week. It did so to accommodate Jewish workers, whose observance of a Saturday sabbath forced them to make up their work on Sundays, offending some in the Christian majority. The mill granted these Jewish workers a two-day weekend, and other factories followed this example. The Great Depression cemented the two-day weekend into the economy, as shorter hours were considered a remedy to underemployment. Nearly a century later, mills have been overtaken by more advanced technologies, yet the five-day workweek remains the fundamental organizing concept behind when work is done. Its obsolescence has been foretold for quite a while now: A 1965 Senate subcommittee predicted Americans would work 14-hour weeks by the year 2000, and before that, back in 1928, John Maynard Keynes wrote that technological advancement would bring the workweek down to 15 hours within 100 years. There’s reason to believe that a seven-day week with a two-day weekend is an inefficient technology: a growing body of research and corporate case studies suggests that a transition to a shorter workweek would lead to increased productivity, improved health, and higher employee-retention rates. The five-day workweek might be limiting productivity. A study in the American Journal of Epidemiology found that those who worked 55 hours per week performed more poorly on some mental tasks than those who worked 40 hours per week. And Tony Schwartz, the author of Be Excellent at Anything, told Harvard Business Review that people work best in intense 90-minute bursts followed by periods of recovery. Taken together, these findings suggest that with the right scheduling of bursts and rests, workers could get a similar amount of work done over a shorter period of time. Moreover, there’s some anecdotal evidence that a four-day workweek might increase productivity. Google’s Larry Page has praised the idea, even if he hasn’t implemented it. And Jason Fried, the CEO of Basecamp, has his employees work four-day, 32-hour weeks for half of the year. “When you have a compressed workweek, you tend to focus on what’s important. Constraining time encourages quality time, ” he wrote an op-ed in The New York Times. “Better work gets done in four days than in five,” he concluded. Beyond working more efficiently, a four-day workweek appears to improve morale and well-being. The president of the UK Faculty of Public Health told the Daily Mail that a four-day workweek could help lower blood pressure and increase mental health among employees. Jay Love of Slingshot SEO saw his employee-retention rate shoot up when he phased in three-day weekends. Following this line of thought, TreeHouse, an online education platform, implemented a four-day week to attract workers, which has contributed to the company’s growth. That said, the five-day workweek might already have so much cultural intertia that it can’t be changed. Most companies can’t just tell employees not to come in on Fridays, because they’d be at a disadvantage in a world that favors the five-day workweek. But there’s a creative solution to this problem. David Stephens, a consultant based in Houston, detailed in a post on LinkedIn the clever system devised at a company he used to work for. The company was divided into two teams. One would work from 7 a.m. until 6 p.m. from Monday to Thursday, and the other would work those hours from Tuesday to Friday. The teams would switch schedules every week, so every two-day weekend would be followed by a four-day weekend. The results, Stephens reports, were positive. The company was open five days a week, from 7-to-6 instead of 8-to-5. He claims that morale skyrocketed. Employees took fewer sick days, visiting the doctor in off hours rather than during the workday. In this scenario, employees still work 40-hour weeks, but they do so over the course of four days rather than five. This arrangement still sounds sub-optimal, though, as working at full capacity for 10 hours is more demanding than doing so for eight. Despite that, the employees at Stephens’s company still preferred 40 hours in four days to 40 hours in five days. They might be even happier—and work even better—if they worked fewer hours in addition to fewer days. Given the ongoing conversation about how most of the old ways are just sitting there, waiting to be disrupted, it’s surprising that the traditional workweek remains wholly intact. On top of that, one would think that the slew of corporate perks deployed to attract top talent would have by now extended to a re-envisioning of the two-day weekend. But it hasn’t. Of course, the upsides of a four-day weekend have yet to be truly borne out, but there’s a lot of evidence that suggests it’s a good idea. So, for now, there appears to be an untapped way for companies to bring on and retain high-quality employees: Shorten the work-week. And figure out a way to do that before everyone else does.