History of GIS Day
A Geographic Information System is specifically designed to manage all of the information involved with interpreting and present geographical data. While this involves a broad number of technologies, they all come down to one thing. Storing and processing data about the world around us and making it available to be used in a format able to be interpreted and used by other systems.
GIS Day was established in 1999 by Esri President and Co-Founder Jack Dangermond after he had been inspired by Ralph Nader to do so. Recognizing the importance and implication of this system, and that it was important that the people of the modern age be familiar with the effect it had on their lives, this holiday was established with the distinct purpose of raising awareness.
While currently primarily used terrestrially, you can bet that when we start putting permanent satellites into orbit around other planets, this technology is going to be vital in driving the study and colonization of the solar system, mining of resources within it, and observing the unique traits of distant planets.