At 7:55 AM (Hawaii Time Zone) on December 7, 1941, the Japanese launched a surprise attack on the United States at Pearl Harbor on the island of Oahu, Hawaii. At around 1:47 PM Eastern Standard Time on the same day, President Franklin D. Roosevelt was meeting with an advisor when Navy Secretary Frank Knox interrupted to deliver the news that the United States had been attacked. The time zones were different in 1941. Hawaii was in a thirty minute time zone and was five and a half hours behind the eastern time zone. That means that the attack happened at 1:25 PM Eastern Standard Time. This means that Franklin D. Roosevelt was alerted of the attack around twenty-two minutes after the first bombs were dropped at 7:55 AM Hawaii time.