At what local time did Japan’s 1945 surrender officially take effect?

Japan’s 1945 surrender officially took effect at 9:25 a.m. Japan Standard Time.

The Japanese Instrument of Surrender was signed aboard USS Missouri in Tokyo Bay on September 2, 1945. The signing began shortly after 9 a.m., with Mamoru Shigemitsu signing at 9:04 and Yoshijirō Umezu at 9:06. Allied representatives then signed, and the formal proceedings concluded at 9:25 a.m.

That time is important because the ceremony itself and the legal conclusion of hostilities were not exactly the same moment. The document recorded Japan’s capitulation, while the completed ceremony marked the official end of the war. News organizations and later histories often simplify the event as happening at 9 a.m., but the precise effective time was 9:25 a.m. JST.

This timing is separate from the August radio announcement. Emperor Hirohito’s broadcast announced Japan’s acceptance on August 15 in Japan, whereas the September ceremony completed the formal surrender process.