NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Is the date ever the same globally?
From: Navastro
Date: 2004 Oct 15, 12:47 +0200
From: Navastro
Date: 2004 Oct 15, 12:47 +0200
Hello, I think that it is correct. I include a figure that will help (I hope) to see it. The figure shows the situation as seen from above the north celestial pole. Best regards, Luis On Fri, 2004-10-15 at 11:37, Jim Thompson wrote: > I need to check my understanding of this with the list. Is this line from a > book correct: > "...at the instant of GMT 1200, the date is the same all over the world"? I > think it is wrong. > > 1. On > http://jimthompson.net/boating/CelestialNav/DatesTimeDiagrams.htm > I tried last year to prove that statement to myself, but was unable to do > so. See > http://jimthompson.net/boating/CelestialNav/TimeDateConversionTable.htm. > Note in that table (I made up this table, so I hope it is right) that when > it is 1200 at Greenwich on day 10 (say), it is is 2400 the previous day in > Time Zone Y (ZD -12), and so it can never be the same date at every place on > the planet at once. The instant it turns to 1200 at Greenwich, the time in > M is 2400 on the same day, but the time Y is 2400 on the previous day > Right? > > 2. There are 25 time zones, not 24, right? The way I see it, that is > because the 15d span of longitude around the IDL is divided into Y (ZD -12) > and M (ZD +12). Although time is always the same in those two "half zones", > date is always different. Am I right? Or is that just splitting hairs to > say that there are 25 time zones, since the time in Y and M is always the > same, even though the date is different? > > (I am working on a CN PowerPoint presentation for teaching, so need to pin > this down.) > > Jim Thompson > jim2@jimthompson.net > www.jimthompson.net > Outgoing mail scanned by Norton Antivirus > ----------------------------------------- >