I have discovered a bug, I think. I went through the bug posts for 2.51 and couldn't find anything like it, but who knows?
To start I am using a fresh install of 2.51. No mods or anything unusual.
I started a single-player race campaign with limited starting tech featuring a humanity that had been conquered and oppressed by aliens for quite a while, before they mysteriously left just as the human resistance was close to defeating their human proxy troops. The humans get their act together and begin exploring the solar system, looking for the aliens, and expanding and building a fleet in case they find them. I pushed this campaign about twelve years down the road, from 2400 to 2412, before stopping because I was considering starting a different campaign with multiple player races.
I created the second game in the same database and played around with it for a bit, but never got much beyond the start phase, mostly due to a crippling Fallout 4 addiction, as my son helped me mod the base game and add a lot of new content.
Either before I created the second campaign or just after I noticed Steve's campaign that comes with the database and I deleted it.
After the Fallout 4 addition abated a bit I felt the need to get back to Aurora, so I opened up the game and decided to go back to my single-race game, as it was farther along and better developed. However, the dates are now screwed up. As noted above, the campaign started at 2400, and went out to March of 2412 before I quit. My log document verifies this. When I opened up the campaign, the dates in the Events window are in August 2068. I checked the image I had made of the starting conditions and that verifies that the campaign started on the year 2400 as well.
I don't know where this date came from. The other campaign I created, with multiple player races, started in the year 1, so it doesn't seem to be cross contamination from that.
I don't know how this happened, and the campaign is essentially unusable because the dates don't match my log document (potential campaign write-up).
Kurt