Mark your calendar for National Plan for Vacation Day on Jan. 31 when Americans are encouraged to plan vacation days for the rest of the year.

According to Project: Time Off, the promoter of National Plan for Vacation Day, 55 percent of American workers don’t use all their vacation time and in 2015 left 658 million vacation days unused.

The organization says: “Taking time off is associated with higher productivity, performance; more positive attitude toward work; increased happiness; improved mental and physical health; better relationships and social life.”

If you want to be more productive, have a better attitude, be happier and healthier, plan to plan your vacation on Jan. 31!