Read this and answer the question. If the question is unanswerable, say "unanswerable".

Before World War II, Guam and three other territories – American Samoa, Hawaii, and the Philippines – were the only American jurisdictions in the Pacific Ocean. On December 7, 1941, hours after the attack on Pearl Harbor, Guam was captured by the Japanese, and was occupied for thirty months. During the occupation, Guamanians were subjected to culture alignment, forced labor, beheadings, rape, and torture. Guam endured hostilities when American forces recaptured the island on July 21, 1944; Liberation Day commemorates the victory. Since the 1960s, the economy is supported by two industries: tourism and the United States Armed Forces.

On what date did World War II start?
unanswerable