You understand the general meaning. However, this was said immediately after the event. (It refers to the Japanese bombing of Pearl Harbor, in Hawaii, on December 7, 1941, and was said by U.S. President Franklin D. Roosevelt in a radio speech to the American people.) He could not know then that everyone would remember that day for a long time after. He thought they would, though. This is his thought, his prediction.
The phrase is used subjectively, where the speaker thinks something is outrageous,and can be used of days or events that have happened or that will happen, both using the future tense:
"On 30 January 1649, Oliver Cromwell had the rightful King of England beheaded, a day/deed that will live in infamy."
"If they ever make England use the Euro, it will be a day/deed that will live in infamy."
"On December 22nd, 1657, Oliver Cromwell banned the eating of mince pies at Christmas, a day/deed that will live in infamy."
 this is true but very few people have ever heard of it.