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Re: JULDAY-CALDAT problem [message #38266 is a reply to message #38265]

Thu, 26 February 2004 06:19

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Luciano writes:

> Hi, maybe somebody has a clue about the following:
>
> IDL> aa=JulDay(11,18,1990,2,0,0)
> IDL> Caldat,aa,m,d,y,h,mi,s
> IDL> print,m,d,y,h,mi,s
> 11 18 1990 2 0 5.3644181e-005
>
> Why does s=5.3644181e-005 and not s=0 as it should be?

I think it is a question of using a computer to do the
calculations rather than your fingers. :-)

Floating point numbers have about 7 significant figures.
Assuming 60 seconds in a minute, this number starts to
vary in the seventh place. So, about as close to zero
as you gonna get, I think.

For a more complete explanation, see this article:

http://www.dfanning.com/math_tips/sky_is_falling.html

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: JULDAY-CALDAT problem By: James Kuyper on Fri, 27 February 2004 08:17
		Re: JULDAY-CALDAT problem By: Paul Van Delst[1] on Fri, 27 February 2004 08:06
		Re: JULDAY-CALDAT problem By: David Fanning on Fri, 27 February 2004 05:28
		Re: JULDAY-CALDAT problem By: lucianor on Fri, 27 February 2004 02:30
		Re: JULDAY-CALDAT problem By: David Fanning on Thu, 26 February 2004 08:51
		Re: JULDAY-CALDAT problem By: David Fanning on Thu, 26 February 2004 08:41
		Re: JULDAY-CALDAT problem By: btupper on Thu, 26 February 2004 08:17
		Re: JULDAY-CALDAT problem By: David Fanning on Thu, 26 February 2004 07:22
		Re: JULDAY-CALDAT problem By: btupper on Thu, 26 February 2004 06:52
		Re: JULDAY-CALDAT problem By: David Fanning on Thu, 26 February 2004 06:19
		Re: JULDAY-CALDAT problem By: Mark Hadfield on Sun, 29 February 2004 14:50

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