1 in 4 workers in U.S. don't get any paid vacation time or holidays

• The United States is the only advanced economy that does not federally mandate any paid vacation days or holidays. 
• About one in four workers in the U.S. don't get any paid vacation time or holidays at all. 
• That particularly affects lower-income workers, part-time employees and small business workers. 

Vacation season is heating up, but for many U.S. workers it may be difficult to take time off. That's because America is the only advanced economy in the world that does not federally mandate paid vacation days or holidays.

Workers in 21 advanced economies, including 16 European countries, Australia, Canada, Japan and New Zealand, are all guaranteed paid time off by federal law, according to a report from Center for Economic and Policy Research, a Washington think tank. 

However, American workers have to rely on their employers to set the minimum, meaning they may not get any paid time off. Indeed, about one in four American workers don't get any paid vacation days or holidays, the CEPR reports. 

And the average U.S. worker in the private sector receives 10 paid vacation days and six paid holidays -- small change compared to what workers in other advanced economies get.

"In the U.S., paid vacation and holiday benefits are based on luck in the boss lottery, not federal policy," said Eileen Appelbaum, co-director at CEPR. "Since we first did this study in 2007, there's been no progress on the national front to catch up with other rich countries."

"We can't depend on the largess of employers to do the right thing," Appelbaum continued. 

Some legislators are working to change that. New York City Mayor Bill de Blasio in January announced a proposal to require employers to give workers 10 days' paid vacation; if it passes, New York would be the first city in the U.S. to mandate paid vacation time.  

Workers in the European Union are guaranteed at least 20 paid vacation days per year, while six European nations — Austria, Denmark, Finland, Norway, Spain and Sweden — guarantee 25 vacation days with an additional 9 to 14 paid holidays.

Spain offers the most total paid days off, with combined 39 vacation days and holidays. Austria follows with 38 total days.

France offers the most in paid vacation, with 30 days, but guarantees just one paid holiday -- for International Workers' Day, or May Day.

Meanwhile, Japan and Canada offer 19 and 25 total guaranteed days, respectively.

But the U.S.? Zero.