The Third War ends in nuclear Armageddon, rendering Earth uninhabitable.
From the destruction of Earth to the dissolution of the Interplanetary Federation of Sol, this is the calendar used by the IFS. This follows the same date structure as A.D., measured from the station Nuntius Terrae. PT begins after the year Earth was destroyed - Jan 1, 1 PT comes the day after Dec 31, 2036 A.D.
The Interplanetary Federation of Sol begins expanding its population into additional colonies and orbiting stations, and forms its first colony on Earth's moon.
Initiated by Emperor Titus Young Sr in the year 2474 A.D., this calendar became the standard for the Sol Empire for the remainder of the Empire's existence. The calendar consists of the same months as the Gregorian calendar. Timescales of minutes per hour, hours per day, etc remain the same. Due to this calendar being a measurement of time since the formation of the Empire, the 1st year of AU technically occurred prior to the creation of the calendar. Additionally, leap years do not exist for this calendar, due to no longer needing to account for planetary orbits.
The Jameson Expeditionary Fleet makes first contact with an alien race identifying themselves as the Dovolish and members of the Varkesh, using an 'old Earth dialect' later identified as English. Tentative communications begin.