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?
Sentence (from "Howard Stern"): 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.
Relevant evidence: No