February 4th, 5th, and 6th are all National Frozen Yogurt Days. It seems to depend on the local yogurt shop which day is celebrated.
Frozen yogurt (yoghurt) is a frozen dessert made with — you guessed it — yogurt. It is not regulated by the U.S. Food and Drug Administration although it is regulated by some states. It may or may not contain live and active bacteria cultures.
Frozen yogurt was introduced in New England, north-east United States, in the 1980s as a soft serve dessert by H. P. Hood under the name Frogurt. In 1998, Brigham’s, a Boston-based ice cream, candy and sandwich shop chain, under the direction of their VP of Marketing & Manufacturing, Jerry Lavely, a food industry innovator, developed and introduced the first packaged frozen yogurt called Humphreez Yogart. 
Originally intended to be a healthy alternative to ice cream, when people complained about the tartness, more sugar was added.
Several yogurt shops including Pinkberry, Yogurtland, and Menchies in Los Angeles have specials (like a free yogurt during certain hours). In 2012, Yogurtland served more than 1.2 million free cups of yogurt on National Frozen Yogurt Day!
Celebrate with goodies from Zazzle