I accidentally set an alarm for 7 PM instead of 7 AM last night, then cooked and ate dinner, watched TV, did the dishes, and finally returned to my room at around 9 PM to discover that my phone had vibrated itself off of my bedside table and was still going 
Every alarm clock that I can recall ever having used, digital or otherwise, has a built-in auto shutoff. Does the iPhone have anything similar?
Every alarm clock that I can recall ever having used, digital or otherwise, has a built-in auto shutoff. Does the iPhone have anything similar?