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Re: Local solar time [message #39964 is a reply to message #39904]

Wed, 30 June 2004 05:59

kuyper
Messages: 5
Registered: June 2004

Junior Member

Craig Markwardt <craigmnet@REMOVEcow.physics.wisc.edu> wrote in message news:<on1xjyrl7b.fsf@cow.physics.wisc.edu>...
> 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.

I don't believe that this definition of "Julian Day" is specific to
the USNO. I believe that they're merely reporting on an international
standard definition. As such, anyone who's using the term correctly is
inherently implying use of UTC, not local time.

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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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