end of a century; fin-de-siècle
Often refers specifically to the end of the 19th century and its associated cultural mood of decadence and anxiety. Can be used for any century's end.
Paris at the end of the 19th century was a center of art.
It's a novel with a fin-de-siècle atmosphere of decadence.
end of the world; apocalypse
Used especially in fiction, games, and speculative contexts to describe a world-ending scenario or apocalyptic setting.
That game is set in a devastated, apocalyptic world.
There was a time when apocalyptic end-of-the-world ideas were popular.
People faced the end of the century with a sense of anxiety.
The game is set in an apocalyptic, ruined world.
This novel is imbued with the decadent atmosphere of the fin-de-siècle.