Since the two Voyager probes launched in 1977 (Voyager I
and Voyager II
), it would be safe to assume that the fictitious Voyager VI launched in that time frame as well. 1977 + "more than 300 years" would suggest at least 2277+; So it's not too hard to extrapolate late 2270's or 2280s from that.
Except the movie came out in 1979 and there wasn't a third probe in development yet. Presumably at that time, the idea was that these were probes that would be launched in the future, not part of some alternate past. There's also the fact that the original "Grand Tour" plan that the Voyager program was scaled down from posited that the third and fourth probes would be launched in '79 -- and we all know how prone these things are to delays (V1 was originally proposed to be launched in '76 but went up in '77). If you look at the Mariner program
spun out of, the general pattern was two probes every 2-3 years.
So if we assume that in the Trek universe as posited by TMP, Voyagers 3 & 4 were launched in, say, 1980, that would mean a launch date of 1982-3 for 5 & 6.
Also -- that's only when it was launched
. Decker said it fell into a black hole more than 300 years earlier. There aren't any black holes in the known Solar system. V1&2 have been in flight for 35 years and they still haven't crossed the heliopause. Even if we assume some hitherto-unknown rogue black hole passed through the outskirts of the system, it still stands to reason that it was lost decades after it was launched -- sometime in the early 21st century at the earliest. Possibly much later.
So really, Decker's line would seem to place the movie squarely in the 24th century. It's not really reconcilable with our modern understanding of Trek chronology. The simplest explanation is that Decker misremembered his history lessons and got the dates wrong.
Except Trek's universe is not ours. We never had orbital nuclear platforms and we certainly didn't have one go off while falling from a failed launch.
While they were a great read thais is the one problem I had with Greg Cox's Eugenics Wars series. Our world cannot lead to the future that Trek has shown us. There's already too many differences. That's not a bad thing. What happens when 2018 rolls around and we don't have a replacement for the sleeper ships we haven't invented yet? What happens when we don't have WWIII (hopefully)? What do we do when the Vulcans don't show up in Montana?
Let Trek be Trek. Don't try to shoehorn it into a timeline that it doesn't fit in.