Task: Question Answering
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. 
Question : When did Oh-My-God particle occurr?
Output (English): 15 October 1991