context: On June 8, 2010, iPhone 4, which adopted iOS 4 and equipped with multitasking functions, was officially announced. On October 4, 2011, , iOS 5 version and Siri were installed for the first time. The iPhone 4S was officially released, and was first sold to Korea. On September 12, 2012, the first iPhone 5 with a 4-inch screen was officially announced, and on September 11, 2013, the iPhone 5C 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: ober 4, 2011