Task: Question Generation
Input (English): Context : The Oh-My-God particle was an ultra-high-energy cosmic ray (most likely a proton) detected on the evening of 15 October 1991 over Dugway Proving Ground, Utah, by the University of Utah's Fly's Eye Cosmic Ray Detector. 
Answer : 15 October 1991
Output (English): The point in time of Oh-My-God particle was what?