Tapani Day was an annual holiday which originated in the Tapani Sector. It was held annually just after the month of Kelona, and before the month of Selona. It was a patriotic celebration highlighted by the use of fireworks and bonfires. It was adopted by many other planets and systems as a celebration of their own cultures and advancements.
Many planets, systems and sectors had adopted Tapani Day, though typically with differing names. The most recognized was perhaps Coruscant, who observed Federation Day (which celebrated the foundation of the Galactic Federation). The holiday was characterized by fireworks and parades, as well as many stores conducting half-price sales (especially on Coruscant). Citizens did not typically work on this day.
While Tapani Day was the traditional name for the holiday, almost every planet had its own name for the celebration. "Patriot's Day" and "High Day" were other common names for the holiday, as well as simply putting the name of a system before "Day".