I don't see how it's the 80's, it seems clear to me it's in the 60's, I can't say a specific year, but with BO being in the 60's, Moon's NML appearing to be in the 60's as well (banner hanging), the plates on the bus say '60 and the 60's era vehicles at Green Run. There's just never been any question in my mind it's in the 60's. I think it's only shortly after the events of Moon and Nuketown, as when you get your first drop, Rich hacks up a lung and says "Sorry, just getting used to the aether" like he hasn't been there long. Maxis's quote about trying for years would still apply as he's been gone since the mid 40's.
Sorry to go off topic. Back OT, Nacht does confuse me a bit as well. The bus driver always mentions Greenbriar Resort (a famous bunker location) when passing the cornfield when I play, so I assume he's alluding the the bunker that is Nacht. The fact the guide calls it the "Prototype" could signify to me that the US has recreated a prototype of the first encounter by US Forces of Nazi Zombies. I was always under the impression when playing the original WaW NDU that it was actually IN Germany. I can't recall the text at the beginning about it, but it was heavily implied.
Now 3arc could've ret-conned NDU into the storyline at Green Run, since there didn't seem to be any story line really developing until SNN, or some say Verruckt (again I think they just ret-conned it in).