Question: When did the sixth season premiere of the show whose 12th episode of that season is called "False Positive"?

Related documents: [0]  [DOC] The sixth season of the American television comedy series "How I Met Your Mother" premiered on September 20, 2010, and concluded on May 16, 2011 on CBS. [END] 
[1]  [DOC] "False Positive" is the 12th episode of the sixth season of the CBS sitcom "How I Met Your Mother", and the 124th episode overall. It aired on December 13, 2010. It features guest star Alex Trebek. [END]  
Answer: September 20, 2010
September 20, 2010