The name V-J Day was modeled on V-E Day, the Allied observance marking Victory in Europe. The “V” stood for victory, while “J” identified Japan; the earlier “E” identified Europe.
Allied governments and newspapers used victory-day terminology as World War II ended on different fronts. V-E Day was observed after Germany’s unconditional surrender in May 1945. When Japan surrendered later that year, the Pacific counterpart became Victory over Japan Day, commonly shortened to V-J Day.
The term can refer to more than one date. Japan announced its acceptance of the Allied terms on August 15, which was August 14 in much of the Americas because of time-zone differences. The formal surrender document was signed on September 2 aboard USS Missouri, and the United States commonly commemorates V-J Day on that date.
This explains why historical references may show August 15 or September 2 without describing different surrenders. One date marks the public announcement; the other marks the formal signing.