Original comic series was in 1989, two years after the first film. The novel versions of Concrete Jungle and Cold War bump the date up to the mid-90s. Also, the third comic book series, Dark River, is entirely ignored.
The comic was definitely not just two years after the first film, that's for certain.
It's funny, we were literally discussing this yesterday on another thread.
Here was my case for 1991:
Yeah, when Rasche says "Christ, it was hot. Hotter than the Summer of 91" its confusing, because he seems to be speaking of it being hotter today than it was in the 1991, even though it's both said in past tense. But then Rauche tells the story of what happened in past tense. "There was nothing romantic that summer." Is he talking about that hot Summer of 1991 or a more current summer?
What has me stick with 1991 is two things. The latest / top of Rauche's back tax returns is 1990. In America the newest is always a year behind.
And then Schaefer says 3 years back Dutch went missing. Often when people count years, they don't count the one they are usually in.
I think it would be less complicated if instead of "Christ, it was hot" in the beginning, he started with "Christ, it's hot" or "there was nothing romantic that summer of '91." But alas...
But that's why I roll with 1991.