Question: What is the date of death of Hamengkubuwono X's father?
Sentence (from "Hamengkubuwono IX"): Hamengkubuwono IX or HB IX; 12 April 1912 – 2 October 1988) was an Indonesian politician and royalty who was the second vice president of Indonesia, the ninth sultan of Yogyakarta, and the first governor of the Special Region of Yogyakarta.
Relevant evidence: Yes