James T. Kirk/Time travel/Earth's 20th century

Kirk and crew visited 20th century Earth on multiple occasions during his captaincy.
In 2267, after experiencing violent time distortions, the Enterprise discovered the source, the Guardian of Forever. McCoy, delusional from an accidental cordrazine overdose, entered the time portal, altering history to the extent that the Federation and the Enterprise no longer existed. Kirk and Spock followed McCoy, appearing in 1930 New York City on Earth. Kirk found himself and Spock shelter in exchange for work, falling in love with a beautiful, idealistic benefactor, Edith Keeler. After Spock discovered that McCoy had prevented history's recorded death of Keeler, he was forced to restrain the doctor from saving her life again while Kirk watched Keeler die and himself avoid doing anything to save her life, the price for restoring the timeline. ()
When the Enterprise traveled back in time from 2267 to Earth of 1969 but was accidentally observed by the United States Air Force, Kirk, with Sulu, beamed down to a military base in Omaha, Nebraska, to destroy photographic evidence of the Enterprises appearance. By warping around the sun's gravity well in a slingshot maneuver, Kirk and his crew managed to rectify the situation, cause the incident to "unhappen," and return to their own time aboard the Enterprise. () While formulating a means of escaping an alternate timeline created by Q's manipulations of the past, Admiral Jean-Luc Picard referenced Kirk's intentional time travels, using this maneuver, prior to attempting it themselves aboard the in visiting the past from 2401. ()
In 2268, Kirk was ordered to repeat the recently proven slingshot maneuver, taking the Enterprise back to 1968 on a mission of historical observation. Intercepting enigmatic agent Gary Seven, Kirk attempted to stop his interference but eventually cooperated with Seven's effort to avert a nuclear exchange between the United States of America and the Soviet Union. () After arriving in 2024, using the slingshot maneuver, Picard recalled Kirk's encounter with Seven after learning of Tallinns similar credentials as a . ()