Original: The 921 earthquake ( ) , also known as the 1999 Jiji earthquake ( ) or simply 921 ( ) , was a magnitude 7.6 earthquake which occurred at 1:47 local time ( 17:47 UTC ) on September 21 , 1999 in Jiji , Nantou , Taiwan .
Simplified: The earthquake happened on September 21 , 1999 at 1:47 am local time ( September 20 17:47 GMT ) .