Convenience store chain 7-Eleven is celebrating its self-appointed birthday Wednesday, July 11 (7/11), with a free slurpee day. They’re going full stop with the theme, too. From 11 a.m. to 7 p.m. today, you can get a free 7.11-ounce Slurpee, while supplies last. The offer applies to any flavor, and there are quite a few to choose from – 7-Eleven boasts over 70 varieties. In addition to standbys like Cherry, Coca Cola, and Blue Raspberry, you can get Dr. Pepper, Peach Dragon Fruit, and something called “KZ3 Battle Fuel.”

The promotion officially runs until 7 p.m., but you may want to get there earlier. According to past patrons on 7-Eleven’s Facebook page, once the special-sized cups run out, it’s all over.

It’s fitting that 7-Eleven celebrates its birthday with ice-based drinks, since ice is what drew customers there in the first place. Started in 1927 in Dallas, 7-Eleven’s original location was at the front of an ice house, where founder Joe C. Thompson started selling milk, bread, and eggs. The ice house’s ability to preserve the food staples made traveling long distance to a grocery store unnecessary, and Thompson expanded the concept to several ice houses in the Dallas area. The name 7-Eleven comes not from the company’s actual birthday, but from its original operating hours: 7 a.m. to 11 p.m. (And in the years before 24-hour establishments became common, such long operating hours were unprecedented.)

7-Eleven expanded quickly, and locations were so prevalent in the second half of the 20th century that the name became a stand-in for convenience stores in general. Following a period of decline in the 1980’s, the chain was spared bankruptcy via a buyout from a large Japanese franchisee, Ito-Yokato. In addition to the Slurpee, which is a registered trademark of 7-Eleven, the chain has gifted society with the Big Gulp and the Super Big Gulp (a 1.2 liter fountain drink).

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The Slurpee, though, is its calling card, and is, like many great innovations, completely accidental. The invention of slushy drinks is credited to Omar Knedlik, a Dairy Queen owner with a broken soda fountain. According to legend, Mr. Knedlik was forced for a time to sell bottled sodas out of his freezer, where the sodas became cold and slushy. Customers loved the consistency, and Knedlik developed the machine that became the ICEE machine. 7-Eleven bought special licensing rights from ICEE in the 1960’s, and as a result today we have free Slurpees, in flavors from Wicked Apple to Pina Colada.

If you can’t get to a 7-Elelven in time for a free slurpee today, never fear: the last free slurpee day at the chain was in late May, so there’s likely another one looming on the horizon.