Hiroshima Day commemorates 6 Aug 1945, the day when an nuclear blast was dropped on the Japanese city town of Hiroshima, followed a few times later by another dropped on the town of Nagasaki.
The bombings successfully finished Globe War II by providing about the surrender of Japan, but at a terrible cost - the two places were damaged, mostly citizens, were approximated at around 200,000, with many more individuals passing away later from injuries and sickness.