1991 is the earliest possible start, and since people want lots of different start dates then let's make 4 different ones, but start the events from 1991 anyway.
The first one begins in 1991 with the dismemberment of the Soviet Union and the break-up of the Warsaw Pact, to give the scenario a "complete" feel and to link it with Vonsson's.
The second one begins in Sept. 11 2001 with terrorists sending the United States on a worldwide witchhunt, to allow people to go into "War on Terror" events without displacing themselves too far from modern times.
The third one changes with every update of the scenario so that it starts right now, today, so that its players can feel they are playing a real modern day scenario.
The fourth one starts in 2012 (need to find the date when the Incas said the world would end) so that people can play more realistically, with the question of nuclear simulation removed entirely.
That will, I am sure, satisfy everyone's needs and (I hope) not be too difficult.