Timeline

This timeline is the work of watching episodes and sometimes a little guesswork. Therefore it might not be 100% correct.

Dated Events
Event	Date	Source Episode
Avatar Kuruk tries to kill Koh, the Face Stealer.	c. -900	The Siege of the North (Part II)
Avatar Kyoshi born.	c. -400	The Warriors of Kyoshi
Avatar Kyoshi kills General Chin and creates Kyoshi island.	c. -370	Avatar Day
Fire Lord Sozin born.	-182	No episode.
Avatar Kyoshi dies.	c. -170	Avatar Escape Online Comic - Kyoshi
Avatar Roku dies.	c. -112	The Spirit World: Winter Solstice Part 1
Aang born.	-112	The Boy in the Iceberg
Conflict between Zhang and Gan Jin begins.	c. -100	The Great Divide
Coming of Sozin's comet, Fire Lord Sozin launches attack on Air Temples, war of conquest begins.	-100	Avatar Roku: Winter Solstice Part 2
Aang runs away and gets frozen in an iceberg with Appa.	-100	The Boy in the Iceberg
Birth of Fire Lord Azulon.	-100	No episode.
Northern Water Tribe city fights Fire Nation soldiers and gets uniforms.	-85	The Siege of the North (Part I)
Kana (Gran-Gran) born.	-80	No episode.
Kana leaves North Pole and goes to South Pole.	c. -60	The Waterbending Master
The Herbalist arrives at the Herbalist Institute in the Earth Kingdom.	c. -40	The Blue Spirit
Death of Fire Lord Sozin, succession of Fire Lord Azulon.	c. -30	Zuko Alone
Aunt Wu arrives at her village in the Earth Kingdom.	-20	The Fortuneteller
Princess Yue born.	-16	The Siege of the North (Part II)
Prince Zuko born.	-16	Avatar Roku: Winter Solstice Part 2
Mai born.	-15	No episode.
Sokka was born.	-15	No episode.
Katara born.	-14	No episode.
Princess Azula born.	-14	No episode.
Toph Beifong born.	-12	The Blind Bandit
Beginning of the 600 day Siege of Ba-Sing-Se.	c. -7	Zuko Alone
End of 600 day siege of Ba-Sing-Se, death of Iroh's son, Lu Ten.	c. -6	Zuko Alone
Death of Fire Lord Azulon, succession of Fire Lord Ozai.	c. -5	Zuko Alone
Haru's village occupied by the Fire Nation.	-5	Imprisoned
Prince Zuko banished after dueling his father.	c. -3	The Avatar State
Katara and Sokka's father depart from their village to help the Earth Kingdom.	-2	The Boy in the Iceberg
Aang released by Katara from the iceberg.	0	The Boy in the Iceberg

Undated Events
Event	Source Episode
Founding of the City of Omashu.	The Cave of Two Lovers
Song's father taken away in Fire Nation raid when Song was a little girl.	The Cave of Two Lovers
A young Lieutenant Zhao serving under General Shu in the Earth Kingdom discovers the Moon Spirit scroll.	The Siege of the North (Part II)
Re-occupation of the Northern Air Temple by the Mechanist and his people.	The Northern Air Temple
Jeong Jeong leaves the Fire Nation military.	The Deserter
Jet's parent killed by Fire Nation when he was 8 years old.	Jet
Fire Nation first attacks on Southern Water Tribe (resulting in derelict Fire Navy ship near Kana's village).	The Boy in the Iceberg
Katara and Sokka's mother killed in a Fire Nation raid.	The Boy in the Iceberg