This day remembers this day in 1941 when the Japanese attacked Pearl Harbor in Hawaii and killed 2,403 Americans during World War 2 in an unprovoked attack. The following day the USA declared war on Japan. It was designated in 1994 by President Bill Clinton on 29th November. The American flag should be flown at half-staff until sunset to honour those who died as a result of the attack on U.S. military forces in Hawaii. It is not a federal holiday.