Forum: Pearl Harbor - Then and Now
Topic: Time differences: then and now
started by: David Aiken

Posted by David Aiken on Dec. 12 2002,10:42
Aloha All,
Of interest, in 1941, Hawaii was in a half hour time zone...different than today...

In 1941, the Pearl Harbor Attack occurred in the harbor area at 7:55 AM in Hawaii when it was 1:25 PM in Washington DC.

Today, they commemorate the attack at 7:55 AM local time in Hawaii when it is 12:55 PM in Washington DC....half hour earlier than fact.

The Japanese used Tokyo time to log in their records. American logs used "Zulu" [Greenwich time] for most logs, yet used local time otherwise. As events in Washington DC are important in Pearl Harbor Attack discussions, this relationship must also be important in any study.

Thus:
0100 Tokyo; 0530 Hawaii, 1100 DC; 1600 Zulu is when the two advance reconn aircraft left the Tone and Chikuma headed for Hawaii.

HTH,
Posted by pjacobsen on Dec. 31 2002,11:46
This unique pre-war and wartime time zone of plus 10 and one-half provided a quick method for us early Japanese naval intercept operators in Hawaii to service our intercepted messages and log entries.

In early 1942, intercept Station H was to be moved from its rather shabby quarters at Heeia on the leeward side of the island to the new base being constructed at Wahiawa. A bomb proof operations building was constructed for the use of the Combat Intelligence unit's operators with the state of the art rhombic antennas and operations such as air conditioning. However, after the Pearl Harbor attack, general service communications confiscated the building for its NPM communications. Combat intelligence intercept was relegated to the south half of the first floor of the main administration building - Building #1. There was no air conditioning and with the blackedout windows, operating conditions were poor to terrible especially with the large numbers of smokers. A few Jury rigged rhomics were installed adjacent to the building to intercept Japanese naval communications.

As I recall, there were two electric clocks set on Tokyo time for the operators to use for the required servicing of messages and log entries. Another was set at GCT time for the HFDF Net and teletype comms to Pearl Harbor and I believe one was set for local time.

Since an operator often had to turn around to see a Tokyo clock sometimes squinting to get the right time, this delay often slowed down the servicing efforts and occasionally something was missed especially for us new operators. I don't know who came up a bright idea that provided a much quicker reference to the required Tokyo time. It may have even been used pre-war at Heeia. Many operators, especially new ones, would wear their watch upside down while on watch. By transposing the 6 to 12 etc. this would give the operator the correct hourly time for Tokyo. Since Hawaii was in zone plus 10 and one-half, the same applied to the minutes. Thus, a quick reference to one's own watch [after being worn upside down] gave the intercept operator the accurate Tokyo time immediately to quickly enter it on intercepted messages and for operator log entries. Of course the day, except for a few early hours right after local midnight, was one day later for logging purposes, but the date was no problem.

It wasn't until mid-1943 that new intercept buildings were constructed on leased Dole pineapple fields at Wahiawa for use by the Combat Intelligence Unit then called Fleet Radio Unit, Pacific or FRUPAC. The much better conditions and more numerous clocks made it much easier to record the required Tokyo time, but a few "older" operators kept up the practice of turning their watches around when going on watch and using it to record the correct Tokyo time on messages and logs.

Never let it be said that sailors were not resourceful.
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