The “V” in V-J Day stands for “Victory” in the phrase Victory over Japan Day.
V-J Day commemorates Japan’s acceptance of the Allied demand for surrender in August 1945. In the United States, celebrations began after President Harry Truman announced the news on August 14, 1945, because the announcement arrived during the evening in Washington. August 15 was the corresponding date in Japan and much of the Pacific.
The term parallels V-E Day, or Victory in Europe Day, which marked Germany’s surrender in May 1945. Together, V-E Day and V-J Day identify the two major victory milestones that ended World War II. The formal Japanese surrender ceremony still took place later, on September 2.
Different countries and time zones used different dates for public celebrations. This is why V-J Day may refer to August 14 or August 15 depending on the source and location, while September 2 remains the date of the formal signing. The phrase does not mean that every Japanese unit surrendered immediately.