According to Woman's World Magazine, National Donut day was started by the Salvation Army in the 1930s as a way to honor women who served donuts to soldiers in WW1. It is held the first Friday in June and you might find deals at your local donut shops to honor the occasion.
Dunkin' Donuts is apparently offering a free doughnut when you buy a beverage today to celebrate the occasion.
Krispy Kreme is also offering free doughnuts.
So grab a cup of Joe and get out there and celebrate!