From Carpe Chaos

Treaty Dates

A "Treaty Date" refers to a date on the calendar that all of the interstellar (tube-traveling) species use as a standard of time when dealing with one another. The calendar begins counting forward at the end of the first interstellar war, which was when the Porgs and the Xotron signed a peace and ethics treaty to establish normal relations between their species. Dates are written as the current era followed by the number of years since the beginning of the current era.