Well, guys, I don’t know why, but I really wanted to figure out the timelines and dates in the Avatar universe — specifically the years and even approximate dates of birth for Zuko’s family and Aang as the Avatar. It took me not a little time, so I'd like to share it with y'all!
Firstly, let me mention some key pieces of information I started with
Zuko was 16 throughout the entire series
Aang was 12 at the beginning and turned 13 during Book 3
Aang was born shortly after Roku died
Roku’s daughter Rina gave birth to Ursa 76 years after Roku’s death
Ursa married Ozai when she was 21
The series starts just before the winter solstice
The series ends in August
That’s all the basic data I had
Now, let’s start with Zuko and Aang’s birthdays!
The winter solstice is on December 21, so the series starts in early December. It is known that the Day of the Black Sun was on August 1, and Sozin’s Comet flew by around the end of August. Since Zuko was 16 throughout the entire plot, his birthday must fall in autumn. Aang was unfrozen at the end of year 99 After Genocide, when Zuko was already 16. Therefore, in 100 AG, Zuko would turn 17. So, Zuko was born in 83 AG
Aang turned 13 around July, so his birthday is in July. Aang was frozen just before the Air Nomad genocide — it was at the end of year 1 Before Genocide — and he was already 12. This means that in 1 BG he turned 12, and in 0 BG/AG he would have turned 13. So, Aang was born in 13 BG
Now, let’s talk about Roku’s family
Roku died at that particular moment when Aang was born, so he died in July in 13 BG. His daughter Rina did not have children for 76 years after his death, which means she gave birth in -13 - 1(year 0) + 76 = 62. So, Ursa was born in 62 AG.
Ozai married her when she was 21, so their wedding was in 83 AG. Zuko was born in the autumn of the same year, so the wedding must have taken place in January, February, or March, and Ursa turned 21 just before she married. So, her birthday is between early January and early March. For simplicity, let’s assume that she was born in January or February :)
Roku’s death - July 13 BG
Aang’s birth - July 13 BG
Ursa’s birth - January/February 62 AG
Ursa and Ozai’s wedding - January/February/March 83 AG
Zuko’s birth - autumn 83 AG
Thank you for reading! Hope it was interesting for y'all! :3