From Star Wars to Indiana Jones - the all-in-one timeline:
What they have done is quite simple: The comic features a Millennium Falcon crashing on earth that is then found 126 years later by Indiana Jones and Short Round. Using this fact as well as that Indy finds the Falcon after the Atlantis story and an estimation of Short Rounds age, a timeline has been created that puts the Battle of Yavin (first Death Star) to the year 1804 (earth time).
|The key panels from "Into the Great Unknown" the Star Wars / Indiana Jones timeline is based upon.|
But in the end this is just a mind game. In the canon core part of the Star Wars universe Han and Chewbacca never vanish and "Into the Great Unknown" is just a little entertaining one-shot comic.