User blog comment:Conqueror of all Zombies/What would you like to see in Battlefield 3?/@comment-2195984-20110206083831/@comment-1427137-20110206134838

Judging from the image and the Teaser, most likely. Could be a bit earlier, like mid-late 1990's, but seeing as there's an Abrams tank, a soldier in modern gear with a modified M4, there's no doubt about it being anytime before the modern era.