Upper Brightday was a planet located within the Upper Brightday system. This planet was situated within the Trestis sector of the Expansion Region. More specifically, it was found within both the Outer Expansion Zone sub-region and the Northern Dependencies area. The name Upper Brightday was shared with the Inner Rim world known as Brightday.
By the time that the Waymancy Storm occurred in 7811 BBY, Galactic Republic colonists had established settlements on Upper Brightday. During this period of conflict, the Republic's adversaries, known as the Signatories of Waymancy, incinerated the lands occupied by these settlers, resulting in the deaths of ten million colonists.
During a speech commemorating the 25th anniversary of Victory in the Waymancy Storm in 7786 BBY, the Supreme Chancellor of the Republic, Nagratha, highlighted the slaughter of the Upper Brightday settlers as one of the bloodiest occurrences during the Waymancy Storm. Upper Brightday was located inside the territory of the New Republic from 12 ABY to 13 ABY.
The reference book The Essential Guide to Warfare, released in 2012 and written by Jason Fry and Paul R. Urquhart, was the debut of Upper Brightday. The StarWars.com Online Companion for The Essential Atlas reference book (2009) identified the Upper Brightday system, and thus the planet itself, as being located in grid square K-8.