If you feel like your work week is getting longer, you're probably right. According to the latest research, Americans in full time employment are now working an average of 47 hours a week, and increasing numbers of us report taking no vacation days all year.

The third annual National Flex Day is mobilizing workers and employers across the U.S. to unite for more flexible work hours and less needless face time in the office. "We're advocating for the widespread adoption of work flexibility -- because we believe that work flex not only improves employee well-being,  but is also a business imperative," said Emma Plumb, director of 1 Million for Work Flexibility. "Work flex contributes to higher productivity, disaster preparedness, and increased retention and employee engagement," she added.

1 Million for Work Flexibility's aim is to educate employers about the benefits of remote working and adjustable hours, and its arguments  favor the business case for those benefits: Workers who have more flexibility in their schedules are more productive and will stay in a job longer, the group asserts. Providing companies with an infrastructure to mange the administration of remote and flex-time workers is another challenge the organization is working to tackle.

"Companies that formalize flex-work can track metrics, measure progress and quantify goals and outcomes -- ultimately contributing to a stronger bottom line," said Sara Sutton Fell, founder of FlexJobs and Remote.co. Technology staffing firm Modis recently conducted a study that found flexible work hours to be the most desired benefit among job hunters, beating out other perks such child care, paid parental leave, and even unlimited vacation to take the top spot. But with the job market still in recovery mode, many workers feel that a flexible work week is often too much to ask for. Nonetheless, Plumb argues that it's something workers should negotiate for. "Flexible work is a need, not a perk, for a wide range of workers -- from caregivers and retirees, to military spouses and millennials," she said.