When Does the Original “Star Trek” Series Season One (1966) Take Place?
"Star Trek" (sometimes released as "Star Trek: The Original Series") season one is a science fiction television show showran by Gene Roddenberry and released September 8th, 1966.
Importantly, it shouldn't be overlooked that the first series pilot "The Cage" was scrapped but later shown on television on October 4th, 1988. This pilot features an Enterprise led by Captain Christopher Pike. Footage from it was used to save money as flashbacks for the first season two-part episode "The Menagerie" establishing Pike as a previous captain of the Enterprise who served just before Captain Kirk. Retroactively, "The Cage" (1988) was absorbed into the Star Trek timeline as a functioning prequel of sorts taking place in the year 2254 AD. Season 1 episode 11 “The Menagerie Part One” clearly establishes the events of “The Cage” seen in video records verbally introduced twice by Spock as “13 years ago”.
It takes place on the fictional Star Trek timeline in the years:
2265 AD - 2266 AD
We know this because in season 2 episode 11 "The Deadly Years" (1967), Captain James Kirk specially says, "I'm 34. I'm 34 years old." and a different scene establishes that Hikaru Sulu has served with Kirk for 2 years, assumedly since the launch of the U.S.S. Enterprise's 5 year mission.
34 - 2 = 32.
The final key is that in "Star Trek: Enterprise" season 4 episode 19 "In a Mirror, Darkly, Part 2" (2005), tiny on a screen labeled "HISTORICAL ARCHIVE: STARFLEET", the bottom line reads, "2233: James T. Kirk is born in Iowa on Earth, March 22."
2233 + 32 = 2265.
Although the famous "stardate XXXX.X" captain's records that open most episodes and some films were mistaken for years on the Gregorian calendar, there is no one-to-one relationship between them. As identified in the biography "Gene Roddenberry: The Myth and the Man
Behind Star Trek": "They marked off sections on a pictorial depiction of the known universe and extrapolated how much earth time would elapse when traveling between given points, taking into account that the Enterprise's warp engines would be violating Einstein's theory that nothing could exceed the speed of light. They concluded that the 'time continuum' would therefore vary from place to place, and that earth time may actually be lost in travel. 'So the stardate on Earth would be one thing, but the stardate on Alpha Centauri would be different,' Peeples says." so they are relative to long distance travel and not an absolute calendar. HOWEVER, actual years on the Gregorian calendar began to be used later.
Additionally, season 1 episode 20 "Tomorrow Is Yesterday" features time travel and sees the crew arrive in 1969 AD. We know this because when the U.S.S. Enterprise arrives in the past, a radio broadcast is heard that states, "This is the 5:30 news summary. Cape Kennedy. The first manned moon-shot is scheduled for Wednesday, 6AM, Eastern Standard Time. All three astronauts who are to make this historic--" before Kirk orders it cut off. The Apollo 11 launch, a three-man spaceflight that included the first piloted landing on the Earth's moon, launched in the real world on July 16th, 1969 AD.
The famous season 1 episode 28 "The City on the Edge of Forever" also features time travel and Kirk and First Officer Spock (officially Spock's surname just falls under "You couldn't pronounce it."; in an expanded element novel it's given as "S'chn T'gai") arrive in 1930 AD. We know this because Doctor Leonard "Bones" McCoy is shown saying, "This looks like old Earth around 1920 or 25." and Edith Keeler replies, "Would you care to try for '30?"
Importantly, it shouldn't be overlooked that the first series pilot "The Cage" was scrapped but later shown on television on October 4th, 1988. This pilot features an Enterprise led by Captain Christopher Pike. Footage from it was used to save money as flashbacks for the first season two-part episode "The Menagerie" establishing Pike as a previous captain of the Enterprise who served just before Captain Kirk. Retroactively, "The Cage" (1988) was absorbed into the Star Trek timeline as a functioning prequel of sorts taking place in the year 2254 AD. Season 1 episode 11 “The Menagerie Part One” clearly establishes the events of “The Cage” seen in video records verbally introduced twice by Spock as “13 years ago”.
2267 - 13 = 2254.
It is the fourth chronological TV show in the Star Trek universe and can be watched at its timeline point. [Expanded elements enrich the experience: it can be watched after reading "Star Trek: Mere Anarchy: Things Fall Apart" (2006).]