What time did the attack on Pearl Harbor start? 7 December 1941, 07:55 HST

Short answer: The Japanese attack on Pearl Harbor began at about 07:55 Hawaii Standard Time on 7 December 1941. That was 17:55 UTC on the same date.

Why 07:55 is the accepted time

The first wave of Japanese aircraft reached the United States naval base at Pearl Harbor on a Sunday morning. Official histories and reference works commonly give 07:55 as the opening time of the attack. Contemporary reports record activity at different locations within a rapidly unfolding assault, so individual logs can differ by a minute or two.

For the ordinary question “What time did Pearl Harbor happen?”, 07:55 a.m. is the best concise answer. It identifies the beginning of the attack itself, not the earlier detection of aircraft or the later damage to a particular ship.

Hawaii Standard Time in 1941 was ten hours behind Greenwich and UTC. Adding ten hours converts 07:55 in Hawaii to 17:55 UTC. The calendar date remains 7 December in both places.

Detection was earlier than the attack

The approaching aircraft were detected by an Army radar station at Opana before 07:00. That did not mean the attack had begun. Radar detection, the first sighting of aircraft over military targets and the first bombs or torpedoes were separate moments.

This distinction explains why some timelines appear to start before 07:55. They are describing warning signs and preparations, not the commonly accepted opening minute of the raid. Historical timelines should say exactly which event their clock refers to.

What unfolded that morning

The attack came in two waves and lasted for roughly two hours. Aircraft struck ships at their moorings and military airfields across Oahu. The battleship USS Arizona was destroyed, USS Oklahoma capsized, and many other vessels and aircraft were damaged or lost.

The United States recorded 2,403 people killed in the attack, including military personnel and civilians. The following day, President Franklin D. Roosevelt addressed Congress and asked for a declaration of war against Japan.

Local time and UTC

• Date in Hawaii: 7 December 1941
• Accepted start of the attack: about 07:55 HST
• UTC: about 17:55 UTC
• Time difference: Hawaii was ten hours behind UTC

Modern readers should not apply the present-day time on a phone without checking the historical offset. Hawaii does not observe daylight saving time today, but historical conversions still need to use the rules that applied on the date of the event.

Why “about” matters

An attack spread across several sites does not have the single physical instant that an aircraft impact has. Watches may not have been synchronized, witnesses were positioned in different places, and reports were compiled after the event. The minute 07:55 is strongly established, but presenting it as a second-level timestamp would imply evidence that the historical record does not provide.

The honest answer is therefore exact to the minute and cautious about seconds: the attack began at about 07:55 local time.

Sources

• Commander-in-Chief, U.S. Pacific Fleet report on the raid
• Encyclopaedia Britannica: When was the Pearl Harbor attack?
• National Park Service: Pearl Harbor National Memorial