The Legend of Korra
Series overview

Season
Season
Book
Episodes
Episodes
Originally aired
Originally aired
Originally aired
Season
Season
Book
Episodes
Episodes
First aired
Last aired
Network
-
1
Book One: Air
12
12
April 14, 2012
June 23, 2012
Nickelodeon
-
2
Book Two: Spirits
14
14
September 13, 2013
November 22, 2013
Nickelodeon
-
3
Book Three: Change
13
13
June 27, 2014
August 22, 2014
Nickelodeon Nick.com
-
4
Book Four: Balance
13
13
October 3, 2014
December 19, 2014
Nick.com

Question: When did the second season of Book Two: Spirits begin airing and on what network?
Answer: The second season (Book Two: Spirits) began airing on Nickelodeon on September 13, 2013.