Question: The season seven of "America's Got Talent", a reality television series, premiered on which date, Judge Piers Morgan left the show after season six and was replaced by radio personality Howard Stern?

Context articles: America's Got Talent (season 6)
Howard Stern
America's Got Talent (season 11)
Australia's Got Talent
America's Got Talent (season 5)
The Howard Stern Show (WWOR)
Howard 100 News
America's Got Talent (season 7)
I Dreamed a Dream: The Susan Boyle Story
The History of Howard Stern

Season six of "America's Got Talent", a reality television series, premiered on May 31, 2011, on NBC.
 The show was hosted by Nick Cannon, while Piers Morgan, Sharon Osbourne and Howie Mandel returned as judges.
 On September 14, 2011, Landau Eugene Murphy, Jr. was announced as the winner of season six.
 This season was the last with Morgan as a judge, as he did not return for season 7, where Howard Stern replaced him.
Howard Allan Stern (born January 12, 1954) is an American radio and television personality, producer, author, actor, and photographer.
 He is best known for his radio show "The Howard Stern Show", which gained popularity when it was nationally syndicated on terrestrial radio from 1986 to 2005.
 Stern has broadcast on Sirius XM Radio since 2006.
 Stern first wished to be on the radio at five years of age.
 He landed his first radio jobs while at Boston University.
 From 1976 to 1982, Stern developed his on-air personality through morning positions at WRNW in Briarcliff Manor, New York, WCCC in Hartford, Connecticut, WWWW in Detroit, Michigan, and WWDC in Washington, D.C. Stern worked afternoons at WNBC in New York City from 1982 until his firing in 1985.
Season eleven of the reality competition series "America's Got Talent" was ordered on September 1, 2015.
 The season premiered on NBC on Tuesday, May 31, 2016.
 Nick Cannon returned for his eighth and final season as host.
 Howie Mandel returned for his seventh season as a judge, while Mel B and Heidi Klum returned for their fourth season.
 Simon Cowell replaced Howard Stern as the fourth judge.
 The live shows began on July 26, at the Dolby Theatre in Los Angeles instead of Radio City Music Hall in New York from previous years.
 Due to the 2016 Summer Olympics broadcast schedule on NBC, the show took a hiatus from August 9–17.
Australia's Got Talent is an Australian reality television talent show which premiered on 18 February 2007 on the Seven Network.
 The show is based on the "Got Talent" series format that originated in the United Kingdom with Simon Cowell.
 The original judges were Tom Burlinson, Red Symons and Dannii Minogue.
 Burlinson and Symons did not return for season four and were replaced by Brian McFadden and Kyle Sandilands.
 Dawn French, Timomatic and Geri Halliwell joined the panel in season seven as replacements for McFadden and Minogue.
 All four judges from season seven will be replaced by Kelly Osbourne, Ian "Dicko" Dickson, Sophie Monk and Eddie Perfect in season eight.
The fifth season of America's Got Talent, an American television reality show talent competition, premiered in the United States on the NBC network and on Canada's Global on June 1, 2010.
 Soul singer Michael Grimm was named the winner on September 15, 2010, beating 10-year-old classical crossover singer Jackie Evancho.
 Piers Morgan and Sharon Osbourne returned as judges.
 After four seasons on the show, David Hasselhoff left to host a new show and was replaced by Howie Mandel.
The Howard Stern Show was an American late-night television variety show, hosted by radio personality Howard Stern.
 It aired Saturdays, beginning at 11:00pm, from July 14, 1990 to August 8, 1992.
Howard 100 News was a radio news team established by American radio personality Howard Stern.
 The group was formed in October 2005 following Stern's announced move from regular radio to Sirius Satellite Radio in 2006.
 From January 2006 until February 2015, Howard 100 News would broadcast an hourly summary of stories related to Stern, his radio show, and those associated with it, on Howard 100 and Howard 101.
 The team was downsized in 2006 and again in February 2015, with only a few staffers remaining to follow the lives of the unusual Stern fans and callers known as "The Wack Pack."
Season seven of "America's Got Talent", a reality television series, premiered on May 14, 2012.
 Sharon Osbourne and Howie Mandel returned as judges.
 Judge Piers Morgan left the show after season six and was replaced by radio personality Howard Stern, as announced on his Sirius XM radio show on December 15, 2011.
 Because of Stern's commitments to his radio program, the live (post-Las Vegas) episodes moved from Los Angeles to the New Jersey Performing Arts Center in Newark, New Jersey.
 The season ended on September 13, 2012, with Olate Dogs announced as the winners of the season.
 This was Sharon Osbourne's final season.
I Dreamed a Dream: The Susan Boyle Story was a one-off television special, starring Scottish singer Susan Boyle, produced for ITV, that aired on 13 December 2009 in the United Kingdom, reflecting the success that Susan Boyle has had since appearing on UK talent show "Britain's Got Talent" and since her debut album, "I Dreamed a Dream", became the fastest selling debut album of all time.
 The show was presented by fellow "Britain's Got Talent" judge Piers Morgan.
 Boyle performing songs from her debut album, "I Dreamed a Dream", including "Wild Horses", "I Dreamed a Dream" and "Cry Me a River".
The History of Howard Stern is a radio documentary series about the life, career and achievements of American radio personality Howard Stern broadcast on Howard 100 and Howard 101 on Sirius XM Radio.
 The ongoing series has featured 35 episodes across four "Acts".
 Each episode includes segments from past broadcasts of "The Howard Stern Show", interviews with Stern's staff and celebrity guests, his family and news reports.
 Narrated by Jim Forbes of VH1's "Behind the Music", the series is produced by "The Tapes Team", a group at Sirius who put together other special programming such as "Mammary Lane" and "Stern Spotlight".