NavList:

   

Reply

There is another interesting error on this page, which says, "There are 25
integer World Time Zones from -12 through 0 (GMT) to +12. Each one is 15? of
Longitude as measured East and West from the Prime Meridian of the World at
Greenwich, England.".

In fact there are 24 zones 15? of Longitude wide, but the zone around the
IDL is split into two 7.5? zones, one on either side of the IDL: M (ZD-12)
and Y (ZD+12).  The time is always the same in M and Y, but the date is
always one day later in M.  So there are in fact 25 time zones, but they are
not all 15? of Longitude wide.

Ships at sea agreed to observe M and Y in an Anglo-French agreement in the
early 1900's, but no land communities observe Y, except perhaps Eniwetok.

The statement in the CPS Student Notes, "at the instant of GMT 1200, the
date is the same all over the world" puzzled the heck out of me, because I
could never prove it using the celestial navigation time conversion rules
taught in the rest of the course, and in Bowditch and Dutton's.  It has
taken me a year to settle the issue in my own mind:
http://jimthompson.net/boating/CelestialNav/CelestNotes/Time.htm#DateSame
as I mentioned in the other post just now.  In short, I believe that the
statement is wrong, at least from a pure navigator-at-sea point of view.

Of course people can chose to observe any date and time they want to, as
long as others understand what they are talking about, and where they are
located.

Jim Thompson
jim2@jimthompson.net
www.jimthompson.net
Outgoing mail scanned by Norton Antivirus
-----------------------------------------

> -----Original Message-----
It does not take into account the differences between DST and Standard Zone
Time - for that look at http://wwp.greenwichmeantime.com/info/timezone.htm

   

Reply