Date: 19 BBY
Location: Coruscant
Combatants: Galactic Empire
Outcome: Establishment of the Galactic Empire Day

History

With the success of Contingency Order 66 and the following extermination of the Separatists Leaders on Mustafar, the Republic fell. In its ashes, the new Galactic Empire rose to galactic dominance.

To celebrate the official declaration of the Galactic Empire, Emperor Palpatine ordered the Imperial forces to parade in all systems of the Galactic Empire to celebrate and demonstrate its strength. Thru the course of a month, the member systems could experience their first Empire Day. After this period, Empire Day will be celebrated every year on the anniversary of the declaration of the Galactic Empire. 

The following day on Coruscant, Mas Amedda, together with a legion of Clone Stormtroopers, oversaw the burning of Jedi corpses and the destruction of their lightsabers to celebrate the start of a new era!

Credit to mocmind for providing us with the main image!