That phrase refers to U.S. President Franklin D. Roosevelt’s description of the Japanese attack on Pearl Harbor on December 7, 1941.
Exact phrase and context
Roosevelt actually said “a date which will live in infamy,” not “a day which will live in infamy,” in his address to Congress on December 8, 1941, asking for a declaration of war against Japan. In this context, “infamy” means lasting dishonor and outrage, so the phrase signals that the attack would be remembered as a shocking and shameful act in history.
Historical significance
The line opens what is often called the “Day of Infamy” speech, which framed the United States as the victim of an unprovoked surprise attack and helped rally public support for entering World War II. Since then, “day (or date) of infamy” has become a common shorthand for Pearl Harbor itself and, more broadly, for any moment of extraordinary disgrace or tragedy.
