Context: The iPhone 4 is a smartphone that was designed and marketed by Apple Inc. Following a number of notable leaks, the iPhone 4 was first unveiled on June 7, 2010, at Apple's Worldwide Developers Conference in San Francisco, and was released on June 24, 2010, in the United States, United Kingdom, France, Germany and Japan. It is the 4th generation of iPhone, succeeding the 3GS and preceding the 4S.

Question: when did the iphone 4 first come out?
Steam of consciousness below:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
The relevant sentence in the passage is: Following a number of notable leaks, the iPhone 4 was first unveiled on June 7, 2010, at Apple's Worldwide Developers Conference in San Francisco, and was released on June 24, 2010, in the United States, United Kingdom, France, Germany and Japan.
So, the answer is June 7 , 2010.