NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
0000 not 2400?
From: Jim Thompson
Date: 2004 Oct 18, 08:01 -0300
From: Jim Thompson
Date: 2004 Oct 18, 08:01 -0300
I am revisting my understanding of how dates change around the world over time (George called time/dates "slithery" -- no better word for it!). I am learning that times and dates, an arbitrary measurement tool applied to our spinning earth for human convenience, must have a set of carefully defined, fixed, arbitrary conventions to work. One example is using Time Zone Y on ships at sea, as agreed upon in 1917 at the Anglo-French Conference on Time-keeping at Sea. But I think it would be safe to say that another convention would be to avoid using the term "2400". Although we can think and write the term "2400", it has no practical meaning, is that right? As soon as the time advances past 23:59:59, then from a navigator's perspective the date changes to the next day, at time 00:00:00. The term "2400" seems to refer to a non-entity, a purely abstract instant of time past 2359 when it is midnight, but the date is still the same day. To resolve that conundrum, I revised the time-date conversion table at http://jimthompson.net/boating/CelestialNav/TimeDateConversionTable.htm by changing the entries from 2400 to 0000, and shifting the date relationships accordingly. But the original version that used 2400 was based on the old US Coast Guard manual, which used 2400. I do not know the historical context of their use of "2400", but today I think 0000 makes more sense. Am I merely catching up with the obvious? Jim Thompson jim2@jimthompson.net www.jimthompson.net Outgoing mail scanned by Norton Antivirus -----------------------------------------
