The fourth season of American talent show competition series America's Got Talent was broadcast on NBC from June 23 to September 16, 2009. Following the previous season, Jerry Springer was forced to leave the program due to other commitments, and was replaced as host by Nick Cannon. A number of changes were also made to the program before filming commenced, which included replacing the "bootcamp" stage with a round similar in format to that used by Britain's Got Talent, changing the Buzzer format to match that being used by the Got Talent franchise, and the live rounds having their results aired in a separate episode the following day – broadcast over a one-hour period and featuring performances by guest stars.