- Stardate 1672.1 (approx. 13 January): While beaming up from planet Alfa 177, a transporter accident splits Captain Kirk into two beings: one "good", who is weak and indecisive, and one "evil", who is overly aggressive and domineering.
- Stardate 1699.0 (approx. 23 January): (TOS: B&B1, "The First Artifact")
- Stardate 1704.2 (approx. 25 January): A strange, intoxicating infection, which lowers the crew's emotional inhibitions, spreads throughout the Enterprise. As the madness spreads, the entire ship is endangered.
- Stardate 1709.1/Reference Stardate 2/0710.21 (approx. 26 January): The vast buildup of Klingon military might reported by Starfleet Intelligence has diverted attention from the long-dormant Romulan Star Empire. While investigating a series of destroyed outposts, the Enterprise discovers a lone Romulan vessel with a cloaking device and a powerful new plasma torpedo. The Enterprise pursues the Romulan bird of prey into the Romulan Neutral Zone, where it picks up images from the Romulan ship's bridge. The Romulans, having never before been seen by Humans, are revealed to visually resemble Vulcans, casting doubt from some on Mr. Spock's loyalty. After taking heavy damage, the Romulan ship self-destructs.
- Stardates 6394.55-6394.75/Reference Stardate 2/0802.11 (11 February): The U.S.S. Republic NCC-1371 investigates a crashed spacecraft on planet BWCC98-IV. The landing party is infected with neural parasites, and the Edoan science officer, Lieutenant Commander Xepesna, destroys all of the ship's astrogation records to prevent the organisms from spreading further.
- Stardate 2124.5 (approx. 27 May): The U.S.S. Enterprise NCC-1701 discovers a rogue planet drifting through space, inhabited by an eccentric being named Trelane who uses his apparently unlimited power over matter and form to manipulate the crew.
- Reference Stardate 2/0811: Spock is promoted to Commander.
- Stardate 2534.0 (approx. 23 November): The crew of the Enterprise visits Ekos, a planet dominated by a Nazi culture and at war with its planetary neighbor, Zeon, while searching for missing Federation historian John Gill.
Captain Kirk's five-year mission was established to have begun in 2265 in the Star Trek: Voyager episode "Q2". The Star Trek episode "The Menagerie, Part I" further establishes that Spock served under Captain Pike for 11 years, and that it had been 13 years since the events of "The Cage," meaning that Stardate 3012.4 fell two years into Kirk's command. The episode "Charlie X" further added weight to this, establishing both Stardate 1533.1 and the Earth date of Thanksgiving, which falls on 23 November in 2265. As the stardates ranged from the mid-1000s to the low 3000s in the first season and continued to increase at approximately 1000 per season afterward, it seems logical to conclude that the first season spanned nearly two years, and later seasons one each, with the second season chronicling the 3000s, the third season the 4000s and 5000s, and the Animated Series the 5000s. If Captain Kirk's command began on or about Stardate 1000, this would put the end of the five year mission on or about Stardate 6000, shortly after the end of the Animated Series. Using these dates as a reference point, the following can be established:
- Stardate 1000 fell on 13 May 2265.
- The range for Stardates each year is from X636 to Y635 (e.g., 1636 to 2635)
- This places "The Menagerie" (Stardate 3012.4) on 18 May 2267, at the beginning of Kirk's third year in command of the Enterprise
- Roddenberry, Gene (Executive Producer). "The Enemy Within." Star Trek, Season 1, Episode 4. Directed by Leo Penn. Written by Richard Matheson. Desilu Productions, 6 October 1966.
- Roddenberry, Gene (Executive Producer). "The Naked Time." Star Trek, Season 1, Episode 6. Directed by Marc Daniels. Written by John D.F. Black. Desilu Productions, 29 September 1966.
- Roddenberry, Gene (Executive Producer). "Balance of Terror." Star Trek, Season 1, Episode 8. Directed by Vincent McEveety. Written by Paul Schneider. Desilu Productions, 15 December 1966.
- McLimore, Guy W. Jr., and Poehlein, Greg K. "Lost and Presumed Dead." Star Trek: The Role Playing Game, Supplement 2214. FASA Corporation. 1984.
- Roddenberry, Gene (Executive Producer). "The Squire of Gothos." Star Trek, Season 1, Episode 18. Directed by Don McDougall. Written by Paul Schneider. Desilu Productions, 12 January 1967.
- Wheeler, Wm. John with McLimore, Guy W. Jr., Poehlein, Greg K., and Tepool, David F. "Cadet's Orientation Sourcebook." Star Trek: The Role Playing Game, Book 2004A. FASA Corporation, 1983.
- Roddenberry, Gene (Executive Producer). "Patterns of Force." Star Trek, Season 2, Episode 23. Directed by Vincent McEveety. Written by John Meredyth Lucas. Desilu Productions, 16 February 1968.