context: On June 8, 2010, the iPhone 4, which adopted iOS 4 and equipped with multitasking functions, was officially announced, and on October 4, 2011, the iOS 5 version and Siri were first installed. The iPhone 4S was officially released, and was first sold to Korea. On September 12, 2012, the iPhone 5, the first iPhone with a 4-inch screen, was officially announced. On September 11, 2013, the iPhone 5C, which is made of five colors of polycarbonate, and the Fingerprint Sensor (Touch ID) The onboard iPhone 5S was officially announced.
question: When was Apple's Siri introduced?
answers.text: October 4, 2011