The United Empire of Earth (UEE) calendar (Standard Earth Year, SEY) is a system of time measurement that is based on the celestial mechanics of the Human homeworld, Earth (Sol III). The year is charted by how long it takes Earth to revolve around the system's sun, and each day (Standard Earth Day, or SED) lasts as long as it takes for Earth to complete a rotation on its axis. While most planets have local calendars, UEE calendar is the official dating system, allowing all its inhabitants to share a common chronology.