According to NationalDayCalendar.com, National Donut Day is celebrated on the first Friday in June every year.

"This day celebrates the doughnut and honors the Salvation Army Lassies, the women that served doughnuts to soldiers during WWI. In 1917, the original “Salvation Army Doughnut” was first served by the ladies of the Salvation Army. It was during WWI that the Salvation Army Lassies went to the front lines of Europe. Home cooked foods, provided by these brave volunteers, were a morale boost to the troops. The doughnuts were often cooked in oil inside the metal helmets of American soldiers. American infantrymen were then commonly called “doughboys.” A more standard spelling is donut." - National Day Calendar

To celebrate this amazing holiday, Dunkin' is offering a free classic donut with the purchase of any beverage. Here's the official invite from Dunkin':

"A day for donuts is a day for America! #DunkOut to Dunkin’ and get a FREE donut with any beverage purchase on #NationalDonutDay, June 7th!"

Some classic Dunkin' donut favorites that are included with this offer:

- Glazed
- Strawberry Frosted with Rainbow Sprinkles
- Chocolate Frosted with Rainbow Sprinkles
- Vanilla Frosted with Rainbow Sprinkles
- Glazed Chocolate Cake
- Boston Kreme
- Jelly
- Old Fashioned

And I'm kinda loving this new emoji that looks like the iconic Dunkin' donut on a refreshing iced coffee: