The burger chain is hoping the shortened week will help attract employees in a tight-labor market.
"Here in Las Vegas, in some of our Shacks, we're testing a four-day work week. That's a big thing. Nobody's really been able to figure that out in the restaurant business," Chief Executive Officer Randy Garutti said at an investor conference last week, as reported by Bloomberg.
"If we can figure that out on scale, it could be a big opportunity," he added. "We're not promising it yet, but it's something we're having fun trying, and seeing how our leaders like it on a recruiting basis and ongoing retention basis."
Some trials involving employees in other industries have found reducing the hours worked per week increased worker productivity and satisfaction.