Empire Day was an annual celebration marking the Declaration of a New Order by Palpatine in 19 BBY and the establishment of the Galactic Empire. The first Empire Day, declared by Palpatine, was a planet-wide celebration on Coruscant that marked both the rise of the Empire and the conclusion of the Clone Wars. After that first celebration, Empire Day became an annual celebration across the Empire. It was still held by the Empire as of 15 ABY. From SW1ki, a Wikia wiki.