Quote Originally Posted by xXHoax View Post
I mean I'd assume в востмидесятых годах denotes the whole action taking place inside the time, rather than including the time among others, such as 1975-1989.
No.
All I can say: they answer different questions:
"В какие годы? - В восьмидесятые."
"В каких годах? - В восьмидесятых."
Idea is almost identical. Difference is very subtle and has no effect for translator. Looks to me like different grammar cases to say the same thing. I do not remember grammar enough to make full analysis. Something like причастие vs деепричастие...