Its interesting that the Japanese had so completely deceived the Americans leading up to the attack on Pearl Harbor. Through the use of radio messages and fleet movements, the American's believed that the Japanese were going to attack American interests soon, but had no strong reason to believe that an attack would happen against a major American base like Pearl Harbor.
Instead Roosevelt and the rest of the US government believed that the imitate attack would happen in South East Asia.
In fact at this point in time, America still believed that there was a chance at a diplomatic solution to the tensions between America and Japan. that would change early on December 7th.
In fact Roosevelt sent one final appeal to the Emperor on December 6th, of course Hirohito would openly smile at receiving the plea from Roosevelt as there was nothing stopping the attack the following morning.
There are pictures from Dec 6th of Pearl Harbor with the Pacific fleet tied up closely together and planes lined up on run ways. The only real tip to a concern on a Japanese attack were anti-submarine nets put up throughout the harbor.
Meanwhile life continued normally in Pearl Harbor as people went shopping and spent time with their families.
President Roosevelt wrote a personal appeal to Emperor
Hirohito to avoid war between the United States and Japan. "Developments are occurring in the Pacific area which threaten to deprive each of our Nations and all humanity of the beneficial influence of the long peace between our two countries." the president wrote. "Those developments contain tragic possibilities ... I address myself to Your Majesty at this moment in the fervent hope that Your Majesty may, as I am doing, give thought in this definite emergency to ways of dispelling the dark clouds. I am confident that both of us, for the sake of the peoples not only of our own great countries but for the sake of humanity in neighboring territories, have a sacred duty to restore traditional amity and prevent further death and destruction in the world."