Japan chiefly remembers August 15, 1945, as the day Emperor Hirohito announced Japan’s surrender.
Hirohito’s prerecorded radio address was broadcast at noon Japan Standard Time. It announced Japan’s acceptance of the terms of the Potsdam Declaration and was the first time most Japanese people had heard the emperor’s voice.
The broadcast did not itself constitute the final signed surrender document. That document was signed aboard USS Missouri in Tokyo Bay on September 2. The difference explains why sources sometimes give two V-J Day dates.
In the United States, the announcement was heard on August 14 because of time-zone differences, while the United Kingdom officially commemorates August 15. Japan calls the date Shusen-kinenbi, meaning a memorial day for the end of the war, though the legal surrender came later.