I'm sorry to zombie this thread, but I thought it'd be better than starting a new one.
I've been thinking about this a lot lately. I do agree that:
Space Seed: 2267
...makes the most sense to me. If we put "Space Seed" 300 years ahead of the year of production, then that puts TWOK around 2282 if we stick straight to "fifteen years." With the bottle of Romulan ale, it has to be at least 2283, and even 2283 would make Kirk and McCoy's exchange mostly ironic. The 2285 year for TWOK has the virtue of allowing the ale a couple of extraordinary years to age, and
makes Morrow's "20 years" line in TSFS make sense, too, in the context of "you started commanding the Enterprise
20 years ago," and jives with the apparent, original "40 years" line.
However, what do we know about the rest of the classic films? TSFS and TVH must take place in short order after TWOK, probably comprising the rest of 2285 and part of 2286. TSFS's opening Captain's long doesn't exactly make clear how much time had passed after TWOK, but long enough for the cadets to transfer off and the Grissom
to head to Genesis, as well as for Valkris to go try to find data on Genesis. Then, Kirks' log in TVH explicitly tells us the crew had been in Vulcan exile for three months. I take this fairly literally, meaning it has been three months since they arrived on the planet during TSFS. TFF seems to take place a bit longer after TVH, but not by much, possibly placing it in late 2286 or early 2287.
For what it's worth, examining stardates, it appears about 100 stardate units passed between TWOK and TSFS, TSFS and TVH, and TVH and TFF. So maybe each movie was about three months apart?
Then we skip ahead to 2293 for TUC. But why 2293? What exactly, explicitly, makes it 2293? Sulu states he'd commanded Excelsior
for three years, which, if TFF is in 2287, could make it as early as 2290. The stardates jump from 8454.1 in TFF to 9521.6 in TUC. That's a difference of 1067.5 units.
If 100 units corresponds to about three months... then that's about 32 months, or just over two and a half years, which is a bit less than Sulu stated, unless he was rounding up.
I think the only other direct chronological reference to the events in TUC is from "Flashback" wherein I believe Tuvok calls them 80 years ago, based I'm sure on the Okudachron.
Something interesting I noticed in TSFS. When Kirk asks Scotty about his progress near the beginning, Scotty says "You'll be fully automated by the time we dock," which garners Kirk's barn door remark. It's never dawned on me until now exactly what Scotty was doing here: he wasn't still fixing battle damage, he was automating the ship to run without all the cadets that the Enteprise
off-loaded between movies. It never occurred to me that when they steal the Enterprise
later, they had already done a chunk of the work to do it at the beginning of the movie.