Today may be Monday, but for plenty of companies, the weekend starts Friday morning—and they say their employees are more productive because of it.

A 4-day—or compressed—work week is offered as an option to at least some employees at 43 percent of companies, but only 10 percent of those companies make it available to all or most of their employees, writes Jeanne Sahadi for CNN Money. She goes on to note that it’s more prevalent at small companies, where 14 percent make it available to all or most of their workers, while only 5 percent of large companies do.

Particularly in the summer, a four-day work week means that employees can be with their families or enjoy outdoor activities without having to take a Friday or a Monday off—and, at the same time, be more focused the rest of the week, despite the nice weather. Extended hours on the other days of the week also mean that employees can concentrate uninterrupted on work for a longer period of time, Sahadi writes.

Some companies go even further by moving to a 32-hour work week of four eight-hour days, typically in the summer. The software company Basecamp (previously called 37signals), for example, goes to a 32-hour work week from May through October, writes CEO Jason Fried in the New York Times.

“Better work gets done in four days than in five,” he writes. “When there’s less time to work, you waste less time. When you have a compressed workweek, you tend to focus on what’s important. Constraining time encourages quality time.” Ryan Carson, CEO of tech education firm Treehouse, also praises the concept.

For organizations where customers might prefer to interact with them during non-work hours, such as doctors and government offices, four-day work weeks mean that offices can be open earlier, or later, than normal business hours.

Similarly, offices that have moved to four-day work weeks find less employee absenteeism. For example, Utah found that overtime and absenteeism were cut by about 9 percent, writes the Associated Press. This is especially true when employees are increasingly using work time for appointments and errands.

Companies with four-day work weeks can also use it as a recruitment or retention tool, writes Jay Love, CEO of Slingshot SEO, in Inc. Alternatively, companies that aren’t in a position to give raises can offer it as a perk instead, writes Thorin Klosowski in LifeHacker.

Four-day work weeks can also reduce employee commute costs. “One day less at work means reduced electricity use and less time spent driving,” writes Lynn Stuart Parramore in Alternet. “Fewer commuters during the traditional rush hours makes travel quicker for everybody, which means less time spent idling in traffic and churning out less greenhouse gases and other pollutants.”

In fact, according to a report from the Centre for Economic and Policy Research, a global shift to shorter working hours could reduce carbon emissions enough to halve additional expected global warming between now and 2100, she adds.

Similarly, four-day work weeks can cut business operational expenditures, writes Lynne Peeples in Scientific American. “For those workplaces, there’s no longer a need to turn on the lights, elevators or computers on Fridays—nor do janitors need to clean vacant buildings,” she writes. “Electric bills have dropped even further during the summer, thanks to less air-conditioning: Friday’s midday hours have been replaced by cooler mornings and evenings on Monday through Thursday.”

Finally, four-day work weeks give employees more time for research and more opportunity to come up with innovative ideas, writes consultant John Boitnott in Inc. “Giving everybody in the company a longer weekend allows them more time to recharge, get out in the world, and stimulate their creative impulses,” he writes. (Fried goes so far as to say that for many people, the office is the worst place to do work.)

That said, a number of organizations—particularly governments—that switched or tested four-day work weeks have stayed with five-day work weeks. For example, Utah switched to four-day work weeks in 2008. But while 82 percent of employees said they preferred the schedule, the state switched back in 2011 because citizens complained about offices not being open on Fridays and savings weren’t as high as projected, writes Vanessa Barford for the BBC. Heating and electrical savings in the first year were projected to be $3 million, but were actually only $502,000, she writes.

Similarly, Virginia considered a four-day work week in 2010, and even tested it out, saying it could save more than $3 million, according to the Washington Post. But it, along with a number of other states that considered it, never ended up making the switch, writes Jessica Mulholland in Governing.

How can you find out if a four-day work week works for your organization? Test it out, writes Stephanie Vozza in Fast Company. “Start by offering the first Friday of every month off, and expand the program to more weeks each month,” she writes. “You’ll realize pretty quickly if you’re losing productivity, but you’ll probably find it didn’t really change anything.”