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Re: Local solar time [message #39969 is a reply to message #39904]

Tue, 29 June 2004 16:36

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

James Kuyper <kuyper@saicmodis.com> writes:

> Craig Markwardt wrote:
...
>> However, I will take issue on your claim that Julian days is a "time
>> system." In fact, Julian day numbers are simply a means of counting
>> whole and fractional days, referred to some offset, but it is the
>> definition of those days that are important!
>
> According to the US Naval Observatory,
> <http://aa.usno.navy.mil/data/docs/JulianDate.html>, Julian days are
> defined in terms of Universal Time, and each one starts at Noon GMT.

Uhh, I'm sorry this is spilling out into the newsgroup. I still
disagree. Whether or not the USNO "definition" includes mention of
GMT or Universal Time, there are in practice enough different ways to
assign days that one needs to explicitly name the time system being
used. My biggest concern for the original poster was whether he meant
Julian days expressed in local time or in UTC, which obviously makes
all the difference in the world for his application.

Craig

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Local solar time By: David Oesch on Mon, 28 June 2004 02:01
		Re: Local solar time By: David Fanning on Wed, 30 June 2004 06:29
		Re: Local solar time By: kuyper on Wed, 30 June 2004 05:59
		Re: Local solar time By: Craig Markwardt on Tue, 29 June 2004 16:36
		Re: Local solar time By: James Kuyper on Tue, 29 June 2004 13:19
		Re: Local solar time By: Craig Markwardt on Tue, 29 June 2004 12:13
		Re: Local solar time By: Craig Markwardt on Tue, 29 June 2004 11:58
		Re: Local solar time By: Craig Markwardt on Tue, 29 June 2004 11:54
		Re: Local solar time By: Michael Wallace on Tue, 29 June 2004 08:28
		Re: Local solar time By: Haje Korth on Tue, 29 June 2004 08:00
		Re: Local solar time By: Haje Korth on Tue, 29 June 2004 05:12
		Re: Local solar time By: David Oesch on Tue, 29 June 2004 05:12
		Re: Local solar time By: Haje Korth on Tue, 29 June 2004 05:09
		Re: Local solar time By: James Kuyper on Tue, 29 June 2004 04:51
		Re: Local solar time By: Craig Markwardt on Tue, 29 June 2004 02:48
		Re: Local solar time By: David Oesch on Mon, 28 June 2004 23:31
		Re: Local solar time By: Craig Markwardt on Mon, 28 June 2004 20:46
		Re: Local solar time By: Haje Korth on Mon, 28 June 2004 08:07

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