Earth-Time

While originally mandated by the United Earth Government, most governments that are primarily Human use it regardless of their feelings towards the UEG. Earth-Time is an approximation of what the current time and date it is in Rome on Earth. Colonies on other planets usually have their own calendars for local concerns, however, Humans always calculate their age based on Earth-Time.
Earth-Time is almost always used in offical documents and in historical records to help keep things making sense to people.