Hellboy

1993-??-??: First appearance in San Diego Comic-Con Comics #2
1997-??-??: Hellboy: The Lost Army [first Hellboy novel]
2002-08-??: Hellboy [P&P RPG - GURPS]
2004-03-30: Hellboy [movie]
2006-10-28: Hellboy Animated: Sword of Storms [cartoon movie]
2007-03-10: Hellboy Animated: Blood and Iron [cartoon movie]
2008-06-28: Hellboy II: The Golden Army [movie]
in future: Hellboy Animated: The Phantom Claw [cartoon movie]

This should cover all the most important events outside of video games, though the life-action movies and the first appearance are perhaps the only ones that really matter. Possibly the publications of award winning comics, but I couldn't figure out their original release dates, so they aren't in this.