V-J Day is the common name for Victory over Japan Day, marking Japan’s defeat in World War II.
The abbreviation means “Victory over Japan,” paralleling V-E Day, which marked victory in Europe. V-J Day has been associated with both the August announcement of Japan’s surrender and the September signing of the surrender document.
In Japan, Emperor Hirohito’s surrender message was broadcast on 15 August 1945. Because of time-zone differences, the announcement was heard in the United States and some other parts of the Americas on 14 August. The formal document was signed on 2 September.
This explains why different countries and sources give different V-J Day dates. The United Kingdom officially commemorates 15 August, while the United States commonly observes 2 September as the formal end of the war.