Events
- An incident occurs between the Federation and the Klingon Empire that results in the two powers becoming mortal adversaries. (TOS: "Day of the Dove")
Notes
- It was previously believed that 2218 was the year in which the Federation made first contact with the Klingon Empire. Events on Star Trek: Enterprise, however, have proven this false.
- Some fans speculate that through the intervention of the Suliban making Klaang crash land in ENT: "Broken Bow" made a change in the timeline and made first contact with the Klingons way earlier.
| 2217 | 23rd Century 2210s |
2219 |