The United States reported Japan’s surrender announcement as occurring on 14 August 1945 because of time-zone differences.
In Japan, Emperor Hirohito’s radio announcement was broadcast on 15 August at noon Japan Standard Time. Because the United States and much of the Western Hemisphere were on the previous calendar date, American news organizations reported the announcement on 14 August. This is why both 14 and 15 August appear in accounts of V-J Day.
The distinction is separate from the formal surrender ceremony. That ceremony took place on 2 September 1945 in Tokyo Bay, when Japanese representatives signed the Instrument of Surrender aboard USS Missouri.
V-J Day therefore does not have one universally used calendar date. The United Kingdom generally commemorates 15 August, while the United States officially observes 2 September as its date associated with the victory over Japan. The date depends on whether the reference is to the announcement or the legal ceremony.