This is a big milestone for any company thinking about making Friday an official day off.

According to findings at Microsoft, allowing employees to only work Monday through Thursday ended up boosting productivity by 40 percent. They tested the theory in Japan through a program they called the Work Life Choice Challenge.

By giving employees there the option to not work on Fridays for an entire month, they compared the results to the same period the year before.

The four-day workweek has long been a staple of newly formed companies, along with the free snacks and coffee and being able to bring a pet to work. It's a change in mindset--you work hard for four days, doing all of the tasks you are assigned and focusing on your efforts over a shorter period of time (but perhaps still working 40 hours).

Then, you take Friday off.

It's all about momentum.

If you complete a ton of work Monday through Thursday, and you have improved the marketing plan or increased sales, or maybe completed all of the accounts payable for the week, and you're totally comfortable with what you've accomplished, it makes sense to then take off the last day of the week and enjoy a long weekend. You've earned it.

Until now, there's not been this kind of support from a large company like Microsoft, where there is actual data to back up the view about productivity. We've read blog posts and books, watched as companies instituted the policy, and maybe even seen some data to convince us, but Microsoft is now going on record as agreeing with the concept.

The test involved 2,280 employees, and more than 90 percent of them reported having an increase in productivity. Interestingly, they also instituted a policy that meetings would only last about 30 minutes. That's important if you're scrunching down the total time people are in the office, since most of them won't even be around on Fridays. The side effect is that meetings became more productive and efficient, mostly because they had to be.

I'm already a fan of the four-day workweek. It makes perfect sense--it's better to focus on completing work anyway rather than forcing people to come into the office a certain number of days, even if they have all of their hours completed and their work is done.

What are your thoughts? Post on my Twitter feed if you have experience skipping Fridays.