Fast-food chain, Chick-fil-A, which specializes in chicken sandwiches and books over $6 billion in annual sales, on Tuesday will celebrate a self-made holiday called “Cow Appreciation Day.” Any adult who comes into one of the restaurant’s locations wearing a cow outfit, or even a cow-spotted accessory, is entitled to a free entree. Children wearing a cow costume can get a free kid’s meal.

#Hashtag holidays, which are essentially made-up celebrations, have become increasingly more common in recent years, as brands give Americans new reasons to market margaritas, martinis, umbrellas, pies, and just about every other consumer good you can think of. With the increased popularity of social media, the reach of these campaigns can greatly increase, especially when there is a tangible promotion involved.

Chick-fil-A has been at “Cow Appreciation Day” for a dozen years now. It’s a nod to the company’s ad campaign, which started over 20 years ago, depicting a black-and-white cow sitting atop the back of another cow painting the words “Eat Mor Chikin” on a billboard. Since then, the cow has been the company’s mascot.

Privately held Chick-fil-A has been a star in the restaurant space. It has reported 48 straight years of sales growth, notching impressive gains in recent years as sales totaled around $3.2 billion in 2009 but nearly doubled over subsequent six years. It helped popularize the chicken sandwich trend, which is a massive market with 2.3 billion breaded chicken sandwiches ordered annually. New rivals have entered the space, including Shake Shack (SHAK) and Boston Market.