Next message: John Simmonds: "Re: 0000 not 2400?"
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
www.jimthompson.net
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