1. See "Avatar Roku, Winter Solstice Part II”, Act III, where Avatar Roku tells Aang, "One hundred years ago, Fire Lord Sozin used that comet to begin the war.”
2. Gyatso was already old when Aang ran away and he died defending the Southern Air Temple, providing direct evidence of the Southern Air Temple’s early destruction. The date of the destruction of the Northern Air Temple is less clear, but the frequent repetition by many characters in different episodes that "airbenders have been extinct for a hundred years” lends credibility to the assumption that the Northern Air Temple’s fall was contemporaneous with its southern counterpart.
3. See "The Storm,” Act II.
4. See Siege of the North, Part I, act I.
5. The derelict Fire Nation ship seen in episodes 101 and 102 had been there according to Katara "since Gran Gran was a little girl.” Additionally, Katara and Sokka’s mother was killed in an undated Fire Nation raid.
6. See "Bato of the Water Tribe”, Act I where Bato tells Katara "No, he and the other warriors should be in the eastern Earth Kingdom by now” when she asks if her father is with him. Further, the placement of the tokens on the map on the floor of the Fire Lord’s war chamber seen in "The Storm” indicates that much of the heavy fighting is around Ba-Sing-Se in the northeastern part of the continent.
7. For example, the village drowned by Jet, the Fire Nation town in "The Deserter” and Haru’s village in "Imprisoned.”