Actually, a while ago I had worked out a rough sketch of Kirk's timeline based off of what was revealed in the episodes themselves.
• 20 years ago he was on Tarsus IV when disaster struck, and witnessed Kodos the Executioner in action (Conscience of the King (S1)). He would have been around 13 (In The Deadly Years (S2) he stated he was 34).
• First met Gary Mitchell when Kirk was still a teenager (Where No Man Had Gone Before (2nd Pilot) he stated he knew Gary Mitchell for 15 years). Arguably, the second pilot might have occured in the year before Season1.
• Mallory’s father helped get him into the Academy (The Apple (S2)) when he was 17 (The Making of Star Trek)
• Lt. Finney was one of Kirk’s Instructors at the academy (Court Martial (S1)), they would become close friends.
• He had to deal with bullying from an upperclassman, Finnegan, during his academy days (Shore Leave (S1)).
• Studied History under John Gill (Patterns of Force (S2))
• Korby’s translation of medical records from the Orion Ruins were required reading. (What Are Little Girls Made Of (S1))
• Garth of Izar’s campaign at Axanar was required reading at the Academy (Whom the Gods Destroy (S3)).
• Cadet cruise, Kirk was part of a peace mission to Axanar for which he was awarded the Palm Leaf of Peace (Court Martial (S1); Whom the Gods Destroy (S3))
• Cadet cruise on the USS Republic (NCC 1371) ‘Ensign’ Kirk reported Lt. Finney for leaving the circuit open to the atomic pile (Court-Martial (S1)). Kirk earns a special commendation while Finney is put at the bottom of the Promotion Lists.*
• Cheated on the Kobayashi Maru test (The Wrath of Khan) possibly as part of his Advanced Command Training*. Something that Spock didn’t take, possibly because he never sought to command a starship.
• First ship: Lieutenant (jg) Kirk is assigned to the USS Farragut, CO is Captain Garrovick.*
• 13 years ago Kirk commanded his first planetary survey mission on Neural where he met Tyree (A Private Little War (S2))
• He contracted Vegan choriomeningitis, but survived (Mark of Gideon (S3)).*
*A supposition that this would occur after his Academy years, as opposed to before or during.
• 11 years ago he was on the USS Farragut when they encountered the vampire cloud (Obsession (S2)).
• Served a tour, when a Lieutenant, as an instructor at Star Fleet Academy. Gary Mitchell was a midshipman in his class. At that time, Kirk enjoyed “long-haired poetry”; was a “stack of books with legs”; and almost married a certain blonde (Carol Marcus? (The Wrath Of Khan)) whom Gary had sent in his direction (Where No Man Has Gone Before (S1)).*
*Probably, in light of the traumatic experience on board the USS Farragut, Kirk was detailed back to the Academy to help him recover (but this is a supposition on my part, but would seem to fit the existing evidence.).
• Prior to gaining command of the Enterprise 4 years ago (S2), Kirk commanded a destroyer-equivalent vessel (The Making of Star Trek), and requested Gary Mitchell as helmsman (Where No Man Had Gone Before (S1)).
• Assumed command of the USS Enterprise from Captain Pike when Pike was promoted to Fleet Captain (The Menagerie (S1)), Gary Mitchell was helmsman, Sulu was in charge of Astrophysics, Dr. Piper is in sickbay, Lee Kelso is Navigator, Scotty was Chief Engineer, and Spock was first & science officer, and Smith was the Yeoman (Where No Man Has Gone Before (S1)).
• USS Enterprise was substantially refitted - to it's season 1 shape.
the G-man Himself