National Vanilla Milkshake Day is celebrated annually on June 20, worldwide. This day honors the classic vanilla milkshake, which has its origins dating back to 1885 when the first milkshakes contained whiskey and were similar to eggnog. By the 1900s, the recipe evolved to include chocolate, strawberry, or vanilla syrup, and in 1922, the modern milkshake was created when an employee at a Chicago Walgreens added ice cream to malted milk. On this day, people enjoy making and consuming vanilla milkshakes, with some opting to add alcohol for adult versions. The celebration encourages individuals to indulge in this sweet treat, emphasizing that the thickness of the milkshake can be adjusted by varying the amount of ice cream used.