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.