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

Context paragraphs:
Sledgehammer (Grey's Anatomy): "Sledgehammer" is the season premiere of the twelfth season of the American television medical drama "Grey's Anatomy", and the 246th episode overall.  It aired on September 24, 2015 on ABC in the United States.  The episode was written by Stacy McKee and directed by Kevin McKidd.  On its initial airing the episode was watched by 9.55 million viewers and opened up to positive reviews from television critics.  Earlier in April 2015, Patrick Dempsey had revealed that he would be leaving the show after the eleventh season despite having signed a contract through another season.  "Grey's Anatomy" centers around a group of physicians struggling to balance their professional lives with their personal lives.

Belles de Jour: "Belles de Jour" is the 66th episode of the CW television series, "Gossip Girl", as well as the season premiere of the show's fourth season.  The episode was written by Joshua Safran and Stephanie Savage and directed by Mark Piznarski.  It originally aired on Monday, September 13, 2010 on the CW.  The episode filmed several scenes in Paris, a move that was heavily promoted by the show's network and commended by critics.  A promotional video entitled "Oh Mon Dieu" used a French rendition of Nancy Sinatra's "These Boots Were Made For Walking" to advertise the season premiere.

How I Met Your Mother (season 6): 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.

Glee (season 5): The fifth season of the Fox musical comedy-drama television series "Glee" was commissioned on April 19, 2013, along with a sixth season.  It premiered on September 26, 2013, as part of the 2013 fall season.  After a winter break, it returned on February 25, 2014, moving to Tuesday nights to finish its season.  The second part of the season featured the 100th episode of the series, the 12th episode of the season, which aired on March 18, 2014.  It was shorter than previous seasons, with twenty episodes instead of twenty-two.

Sliding Bobs: "Sliding Bobs" is the first episode and season premiere of the sixth season of the animated comedy series "Bob's Burgers" and the overall 89th episode; it is written by Greg Thompson and directed by Don MacKinnon.  It aired on Fox in the United States on September 27, 2015.  In the episode, Bob begins to notice that he is losing hair from his moustache, and Linda tells how important his moustache was in their meeting.  The kids then tell their own versions of how Bob and Linda would have met, if Bob didn't have a moustache at that time.

List of All-Stars and Pahkitew Island episodes: This is a list of the episodes for "Total Drama All-Stars" and "Total Drama: Pahkitew Island", two segments which make up the fifth season of the "Total Drama" series, a Canadian animated television series.  This season is a sequel to "Total Drama Island", "Total Drama Action", "Total Drama World Tour", and "".  This season also features the 100th episode of the whole series, which aired in Canada on February 27, 2014.  The series' 100th episode is the 9th episode of this season which is called "Zeek and Ye Shall Find".  The first episode was the highest viewed telecast on Cartoon Network for the week of the season premiere.  This season is twenty-six episodes long, each episode twenty-two minutes in length, excluding commercials.

Hopeless (True Blood): Hopeless is the sixth episode of the fifth season of HBO's original series "True Blood" and the 54th episode overall.  It was first shown on TV on July 15, 2012 and was directed by Dan Attias and written by Alan Ball, creator of the series.  The episodes of the series are based on the Charlaine Harris books, The Sookie Stackhouse novels whereas the episodes of the season are based on the fifth book in the series "Dead As a Doornail (book)" which follows the Shifters being murdered whereas in the season fang bangers and shifters are being hunted.  Even so, the plot of the book is only one of the minor subplots.  The episode primarily follows Bill and Eric who must now face Russell again after Roman is killed by him; Sookie and Jason go to a faery club where their family's dark history and greatest secrets are revealed to them.  Meanwhile, Sam volunteers to assist Andy with a case.  The episode was precceeded by "Let's Boot and Rally" and was followed by "In the Beginning", which picks up the events of "Hopeless."  The episode received fair reviews from critics.  The episode ended several minutes earlier than the timeslot filled, as it was about 50 minutes or so, which notably also happened in "Let's Boot and Rally".  Stephen Moyer will pick up the events of In the Beginning.  As of 2012 the episode has received the most ratings only behind by the season premiere episode "Turn, Turn, Turn! "

Game On, Charles: "Game On, Charles" is the first episode of the sixth season of the American mystery drama series "Pretty Little Liars", and is the 121st episode overall.  It originally aired on June 2, 2015, ABC Family and serves as the season premiere of the sixth season.  The episode was directed by Chad Lowe and was written by showrunner I. Marlene King and Lijah J. Barasz.

False Positive (How I Met Your Mother): "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.

Fashion Queens: Fashion Queens is an American fashion-based talk show that aired on Bravo.  The series premiered on March 17, 2013, with a three-week trail run.  "Fashion Queens" is hosted by Bevy Smith, Derek J, and Lawrence Washington.  Derek J and Lawrence Washington have both made several appearances on "The Real Housewives of Atlanta".  Following the series' three-week trial run in March 2013, the first season continued on April 14, 2013.  The second season premiere on November 3, 2013, which coincided with the sixth season premiere of "The Real Housewives of Atlanta". "  Fashion Queens" was filmed in New York City.

Supporting paragraphs: False Positive (How I Met Your Mother) How I Met Your Mother (season 6)
Answer: September 20, 2010