Hober Mallow wrote:
Not to derail the thread, but I'm just wondering if there are any similar letters or memos indicating the time period in which the series is set. Something like, "I noticed a mistake in 'Space Seed' setting STAR TREK in the 22nd Century when we recently decided the show was set in the 23rd Century; no need to change anything, just be aware for future episodes."
The time frame of the series was kept intentionally vague, since they didn't want to make any firm assumptions about the rate of technological progress. That's why they invented the deliberate gibberish of stardates. But mostly the estimates did tend to hover around 2-300 years in the future, with "The Squire of Gothos" being the one outlier (placing the series in at least the early 28th century, since Trelane was 900 light-years from Earth and aware of things from the early 19th century).
However, the second-season writers' guide (the only one I have a copy of) does mention that the time frame is "actually about two hundred years from now." I wouldn't be surprised if that was added to the revised guide based on what "Tomorrow is Yesterday" and "Space Seed" had established.
I believe the earliest reference to ST being in the 23rd century was probably in The Making of Star Trek