Still, not everyone thinks a four-day workweek is good news. Some voice concerns that longer days in the office might lead to increased exhaustion and sickness, less time for working out as well as more frequent stops at fast food restaurants. So far, however, surveys suggest otherwise. "Utah employees actually show decreased health complaints, less stress and fewer sick days," Wadsworth says, noting previous research finding that fatigue is typically triggered by workdays over 12 hours. Early results from another multicity survey indicate that just 20 percent of respondents said they felt they ate more fast food and only 30 percent said they worked out less. In fact, 30 percent said they exercised more. Anecdotal evidence from Utah also points to an unexpected benefit: increased volunteerism.

As the yearlong experiment with this new model nears its end next month, employees of the cities of El Paso, Tex., and Melbourne Beach, Fla., among others, are following Utah's lead with their own TGIT trials. Struggling automakers have also spotted the potential savings. Starting August 10, General Motor's plant workers in Lordstown, Ohio, will work four 10-hour days a week. (It was the car industry—Henry Ford, in particular—that made the five-day 40-hour workweek standard back in the 1920s and 1930s. Organized labor also helped drive federal legislation that in 1940 locked in a 40-hour week from what had commonly been more than 50 hours, and also banned child labor.)

New York, a state with higher energy costs and a workforce approximately 10 times larger than Utah's, might especially benefit from a four-day workweek, according to Michael N. Gianaris, a Democratic member of the New York State Assembly. Dealing with a "massive budget deficit," the state continues to look for "innovative ways to save money without causing pain to existing programs and raising taxes," says Gianaris, who introduced legislation to test the schedule among state employees. He sees growing momentum for the idea, which boasts "very little downside and a whole lot of upside."

"As we move further into the 21st century, governments need to look for ways to become more efficient. Moving to a four-day workweek should be at the top of the list," Gianaris says. "It helps the environment. People like it. It's a no-brainer."