O'Grady also said, "[A]s new tech grows, everyone should get richer."

In earlier centuries, workers had to fight for things like the eight-hour workdays, O'Grady points out, which was also the case in the U.S. Now, in the 21st century, "a time of rapid industrial disruption" according to O'Grady, it's time to set our sights on the shorter work week "to take back control of working time," she said.

"I believe that in this century, we can win a four-day working week, with decent pay for everyone," O'Grady said during a speech at the TUC's annual gathering in Manchester, England on Monday.

That's according to Frances O'Grady, the general secretary of the Trades Union Congress , an organization in the United Kingdom representing labor unions.

O'Grady's comments add to recent buzz about the feasibility of a shorter workweek.

Serial entrepreneur Richard Branson said advances in technology mean that workplaces can reconsider the traditional five-day work week.

"Ideas such as driverless cars and drones are becoming a reality, and machines will be used for more and more jobs in the future. Even pilot-less planes will be become the reality in the not too distant future," Branson wrote in a blog post in January.

"On the face of it, this sounds like bad news for people. However, if governments and businesses are clever, the advance of technology could actually be really positive for people all over the world. It could help accelerate the marketplace to much smarter working practices," Branson said.

In particular, technology enables people to work when and where they want, says Branson, a practice Virgin managers are encouraged to embrace, according to his blog post. Technology can also increase the efficiency of work, said Branson and that means people could work fewer hours.

"Many people out there would love three day or even four day weekends. There are many people out there who would want to job share, and would love longer holidays. Everyone would welcome more time to spend with their loved ones, more time to get fit and healthy, more time to explore the world," Branson says. "By working more efficiently, there is no reason why people can't work less hours and be equally – if not more – effective."

Similarly, Microsoft co-founder Bill Gates has said advances in artificial intelligence will lead to longer vacations. "More free time is not a terrible thing," Gates told FOX Business Network at the World Economic Forum in January.

And Perpetual Guardian, a 240-employee New Zealand firm that manages trusts, wills and estates, recently garnered attention for conducting a two-month trial where employees worked four days a week at their regular five-days-a-weekk pay. It was considered a success: Staff stress levels lowered 7 percent, and 78 percent said they could manage work-life balance, from only 54 percent pre-trial.

Plus, the change created good will. "Many employees see the reduced working hours as 'a gift' and 'a privilege not a right,' and feel a deep sense of goodwill and reciprocity towards the organization, which manifests in an openness to 'go the extra mile' and think about 'what I can do to give back,'" says the resulting qualitative analysis from Dr. Helene Delaney from the University of Auckland Business School. "Many employees reported a willingness to be available for work purposes on their day off."

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