No documented founder or formal establishment record has been identified. The observance emerged from the Harry Potter fan community, catalyzed by Pottermore's House Pride Week events beginning in November 2012, with the March 22 date appearing by 2014.
CHAPTER 01
From 500 Copies to a Global Franchise
When Bloomsbury published Harry Potter and the Philosopher's Stone in June 1997, the first print run totaled just 500 hardback copies, 300 of which were sent directly to libraries. The modest debut gave no hint of what followed. By the release of the seventh book a decade later, the series had become the best-selling book series in history.
Warner Bros. adapted the novels into eight films starting in 2001. The franchise expanded further with theme parks in Orlando, Osaka, and Beijing, along with the Warner Bros. Studio Tour in London. Together, these extensions cemented the Hogwarts houses as cultural shorthand for personality types far beyond the reading audience.
