Microsoft tested out a four-day work week in its Japan offices and found as a result employees were not only happier – but significantly more productive.

For the month of August, Microsoft Japan experimented with a new project called Work-Life Choice Challenge Summer 2019, giving its entire 2,300-person workforce five Fridays off in a row without decreasing pay.

The shortened weeks led to more efficient meetings, happier workers and boosted productivity by a staggering 40%, the company concluded at the end of the trial. As part of the program, the company had also planned to subsidize family vacations for employees up to ¥100,000 or $920.

“Work a short time, rest well and learn a lot,” Microsoft Japan president and CEO Takuya Hirano said in a statement to Microsoft Japan’s website. “I want employees to think about and experience how they can achieve the same results with 20% less working time.”

In addition to the increased productivity, employees took 25% less time off during the trial and electricity use was down 23% in the office with the additional day off per week. Employees printed 59% fewer pages of paper during the trial. The vast majority of employees – 92% – said they liked the shorter week.

The experiment is not the first time long weekends have been experimented with in the corporate world. In 2018, New Zealand trust management company Perpetual Guardian trialled a four-day work week over two months for its 240 staff members. Employees reported experiencing better work–life balance and improved focus in the office. Staff stress levels decreased by 7%.

Workers have often said they could be more productive with less time in the office. A survey of 1,500 workers and 600 human resources managers by HR consulting firm Robert Half found 66% of workers said they wanted to work less than five days a week.

Another experiment published by the Harvard Business Review shows shorter work days, a decrease from the average 8-hour work day to a 6-hour work day, increased productivity. A 2018 survey of 3,000 employees by the Workforce Institute at Kronos found more than half of full-time workers thought they could do their job in five hours a day.

Microsoft Japan’s challenge was just a pilot project, the company told the Guardian in a statement, and it’s unclear if these changes will be implemented in offices elsewhere or on a longer term basis. It plans to implement another iteration of the challenge this winter.

“In the spirit of a growth mindset, we are always looking for new ways to innovate and leverage our own technology to improve the experience for our employees around the globe,” a Microsoft spokesman said.