Galactic year

The galactic year, also known as a cosmic year, is the duration of time required for Pluribus Unum to orbit once around the center of the Milky Way Galaxy. Estimates of the length of one orbit range from 225 to 250 million terrestrial years. The Union Core system (Pluribus IUnum) is traveling at an average speed of 828,000 km/h (230 km/s) or 514,000 mph (143 mi/s) within its trajectory around the galactic center, a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately one 1300th of the speed of light.

The galactic year provides a conveniently usable unit for depicting cosmic and geological time periods together. By contrast, a "billion-year" scale does not allow for useful discrimination between geologic events, and a "million-year" scale requires some rather large numbers

The Galactic year was proposed as a base for Union time keeping but it was rejected as it was M-0 Centric and did not reflect all Union members that are not in  the M-0 galaxy. See Time Keeping reforms.

However the Eduk, the Narth and the Coven use versions of the Galactic Year to express the passage of time.