I'd take that as accurate due to his intellegence.
In that case, you'd have to take it as accurate that the movie happened in the 2190s, too, since he says he was prince of millions 200 years prior.
OTOH, we can take that as inaccurate due to his egotism. It can be easily argued that the 1990s were 200 years in Khan's past as of the 2280s - from Khan's own point of view, distorted by time dilation during his sublight voyage. It can similarly be argued that an event 18x365 Earth days old is exactly 15 years in the past - from Khan's own point of view based on the length of the Cetian year...
How good can it be if it was just made this year?
Well, if it's
ale, then anything from some bygone year would be suspect - and only worth drinking if one knew that the current stock was based on an inferior recipe and last year's stock, despite being so old, still had a superior taste for that reason.
If the mention of a year gives our hero a pause, then it's most probably evidence that it's not the current year.
..since TSFS took place immediately after TWOK and therefore the giant Space Dock had to have already been built by TWOK. So that narrows that down.
What is narrowed there? We can assume the Spacedock was built e.g. two centuries before Kirk's birth quite regardless of what is said or shown in the movie (or for all we know, two thousand years before, by Vulcans, and later towed to Earth). Absence of Spacedock from earlier shots is no evidence of nonexistence, because space is big and the camera field of view is narrow and centered on our heroes.
Regardless, just because we don't see it being built or in use in TMP doesn't mean it wasn't.
Or in TOS, for that matter.
We get no indication that Spacedock would be capable of refitting, building or overhauling starships. That's what ST:TMP and ST2:TWoK involve, so naturally some other type of installation is seen performing those tasks.
And while I will always be in the camp that ST TMP took place approximately 2.5 years (2272/3) after the 5 year mission, that is only because of Decker's statement about Kirk not logging a single star hour in 2 and a half years, and by Kirk's defence that he was out there with 5 years experience (that I assume he was specifically refering to as in a command position). He was refering to the great 5 year mission of TOS because that's what the audience would have been familiar with.
Those things give us a minimum temporal distance between TOS and TMP. OTOH, Decker's later line gives a greater minimum requirement: he claims Voyager 6 was launched over 300 years prior. If we assume Voyagers 1 and 2 were launched at the same time in both the Trek universe and ours, and Voyager 6 was launched later than Voyagers 1 and 2, then the movie must take place in 2278 or later, thus probably a decade after TOS rather than just 2.5 years.
Of course, even if the Trek space program wasn't more advanced than our own by several decades, Voyager 6 might still have been launched before Voyager 1. After all, Voyager 2
was launched before Voyager 1...
Timo Saloniemi