copied directly from - http://alisachristopher.deviantart.com/journal/15607110/#journal
If you haven't already seen:
[link]We have confirmed with Nickelodeon that season three of Avatar will have 21 episodes, rather than the 20 episodes that seasons one and two had.
The "Day of Black Sun" movie event is two separate episodes broadcast together, somewhat analogous to the way "The Secret of the Fire Nation" event was handled in the second season. The two episodes for the "Day of Black Sun" are episode 310, "Day of Black Sun Part 1: The Invasion" and episode 311, "Day of Black Sun Part 2: The Eclipse".
Although the episodes are separate (numbers 310 and 311 respectively), both are part of "Chapter 10" in Book Three: Fire. Up until now, each chapter has been an episode, but with "Day of Black Sun" this is no longer the case.
Also revealed was that the Avatar season three (and show) finale will be comprised of episodes 318, 319, 320 and 321. No other information on episode titles or broadcast dates was available.
------
So 310: The Invasion and 311: The Eclipse, but Chapter 10: Day of Black Sun.
So that 312: The Western Air Temple = Chapter 11.
Oy for numbering. Whatev.
But Four Part Finale. Whoo. That's a 2 hour Finale, just like the big boys in one hour programming.
As of yet, there's been no airdate scheduled for 312: The Western Air Temple. But Rumors place it sometime in Late January or February. According to *rufftoon, the Final Audio mix is still being worked on for some of the episodes. But that's good news, in that the Final Audio Mix is the Last part of the editing process.