The log of USS LSM-87 begins at 0800 on Sunday, October 15, 1944. This was ship’s time, which at the moment was the local time and date in Houston.

The problem with using times and dates from the ship’s log is that the ship observed naval time, which was defined by the 1917 Anglo-French Conference on Time-keeping at Sea. In a nutshell, the 180° meridian established the naval date line (which is not the same as the International Date Line), and the 24 naval time zones were then set by 15°-wide longitudinal (pole-to-pole) gores. Ships were to observe the standard time of a country when within its territorial waters, but then use naval time when at sea.

From January 20, 1942 until September 25, 1945, the United States observed “war time”, which was year-round daylight savings time. So the ship’s initial log entry corresponded to 0800 Central War Time (CWT), 0900 EWT, and 1300 Zulu (or GMT, which is now referred to as UTC).

Of course, the ship moved westward until September 1945 and the officers adjusted the ship’s clock accordingly. LSM-87 crossed the naval date line westbound at roughly 2359 (just before midnight) on the evening of February 8, 1945 – a ship’s time that corresponded to 1159 Zulu, 0759 EWT, and 0659 CWT February 9. Upon crossing the line, the ship’s clock was advanced by one full day, so there is no ship’s log entry for Friday, February 9 1945. One minute after crossing the naval date line, the ship’s clock read 0001 on Saturday, February 10 1945. This corresponded to 1201 Zulu, 0801 EWT and 0701 CWT on Friday, February 9 1945. Similarly, the ship’s log includes two full entries for Sunday, December 16 1945 as the ship’s clock was set back by one day upon the eastbound crossing of the naval date line.

A further complication is that ships calculate GMT (Zulu) from the local time zone, and not vice-versa. So the ship’s initial log entry states the time zone as “Plus 5”, even though Houston time was GMT minus 5. “Plus 5” means “add 5 hours to arrive at Zulu time; GMT-5 means “subtract 5 hours from GMT to arrive at local time”.

So for purposes of this re-enactment, I will number the ship’s days consecutively, with new days beginning at midnight on the ship’s clock. Any times given will be the time on the ship’s clock. When informative, I will also provide Zulu, EWT, and EST times and dates.

I publish Tweets at the exact minute of the entry in the ship’s log (plus 75 years).