Founding Day
Prior to its annihilation in 0 BBY, Alderaan, a Core World, observed Founding Day as a special occasion. This holiday served as a remembrance of the establishment of the House of Organa, the Human royal lineage of Alderaan, whose roots stretched back to the planet's colonization in 27,500 BBY. A key feature of Founding Day celebrations was the display of fireworks.
Behind the scenes
Karen Miller's 2008 novel, The Clone Wars: Wild Space, included a reference to Founding Day.