U.S. newspapers commonly used August 14, 1945, for V-J Day because of the time difference with Japan.
Emperor Hirohito’s surrender announcement was broadcast in Japan shortly after noon on August 15. At that moment, it was still August 14 in the United States and much of the Western Hemisphere. President Harry Truman announced the news to Americans, and celebrations quickly spread through U.S. cities.
This creates a genuine date difference rather than a disagreement about the event. Japan and many other countries commemorate the announcement on August 15, while American historical references often use August 14. September 2 is a third important date: it marks the signing of the formal surrender document in Tokyo Bay.
The phrase V-J Day therefore has more than one date in historical usage. A question that does not specify the region or event can be ambiguous. This question specifies U.S. newspaper usage and the time-zone reason, making August 14, 1945, the intended answer.