At the time, and during the lifetimes of Walt and Roy Disney, July 17 was considered a preview, with July 18 the official opening day. Since then, aided by memories of the television broadcast, the company has adopted July 17 as the official date, the one commemorated every year as Disneyland's birthday.

Disneyland’s "birthday" is July 17, 1955. Located in Anaheim, California, the park was the brainchild of Walt Disney and represented a radical departure from the traditional amusement parks of the era. The opening day, often referred to as "Black Sunday," was famously chaotic; the park was overcrowded due to counterfeit tickets, a heatwave melted the fresh asphalt, and a plumbers' strike left water fountains dry. Despite these initial hurdles, the park became a global phenomenon and essentially created the modern theme park industry. Every year on July 17, the Disneyland Resort celebrates its anniversary with special parades, commemorative merchandise, and tributes to Walt’s original vision for "The Happiest Place on Earth."