How long did we fight the Japanese during World War 2?

Assuming "we" is the US, the war started on December 7, 1941 (December 8 in Japan) with the attack on Pearl Harbor and ended with the Emperor Hirohito's radio address that Japan accepted the terms of the Potsdam Declaration on August 14, 1945 (August 15 in Japan). There were scattered actions after the announcement because it took a while for the news to be transmitted to all the forces in the field on both sides, in addition, some barbaric Japanese individually or as units committed atrocities such as the murder of prisoners and civilians upon learning of the surrender.

The surrender was signed at Tokyo Bay on September 2, 1945.