From: JiangZiqiang <zqjiang86_at_nyahnyahspammersnyahnyah>

Date: Sat Nov 05 2011 - 10:26:14 MDT

Date: Sat Nov 05 2011 - 10:26:14 MDT

Dave, Now, I understand that Base units of "years" and "months" are dangerous.And I don't understand that "This function does not return the correct minutes

and seconds if the reference time doesn't start at minute=0, second=0." can you give me an example? thanks you

Ziqiang > Date: Sat, 5 Nov 2011 00:25:51 -0600

*> From: dave.allured@noaa.gov
*

*> Subject: Re: cd_calendar problem
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*> To: zqjiang86@hotmail.com
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*> CC: ncl-talk@ucar.edu
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*>
*

*> Two problems.
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*>
*

*> (1) Read in description of this function, under "Caveats":
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*>
*

*> "This function does not return the correct minutes
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*> and seconds if the reference time doesn't start at
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*> minute=0, second=0."
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*>
*

*> (2) Base units of "years" and "months" are dangerous with real time
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*> calendars. Both are variable length. Years can be 365 or 366 days.
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*> Months can be 28, 29, 30, or 31 days. Some software defines
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*> "years" and "months" as long term averages. Results are
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*> inconsistent between different calendar dates, and between software
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*> packages.
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*>
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*> For best results, always use constant time base units of days,
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*> hours, minutes, or seconds. For example:
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*>
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*> x = 365 * 3 + 366 * 2
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*> x@units = "days since 2011-12-31 12:00:00"
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*> print(cd_calendar(x,0))
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*>
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*> x = 24 * (31 + 29 + 31 + 30 + 31)
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*> x@units = "hours since 2011-12-31 12:00:00"
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*> print(cd_calendar(x,0))
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*>
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*> --Dave
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*>
*

*> On 11/4/2011 11:02 PM, JiangZiqiang wrote:
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*> > Hello,
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*> >
*

*> > when I used function "cd_calendar", right result was not got. why?
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*> > x = 5
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*> > x@units <mailto:x@units> = "years since 2011-12-31 12:56:58"
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*> > print(cd_calendar(x,0))
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*> > x = 5
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*> > x@units <mailto:x@units> = "months since 2011-12-31 12:56:58"
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*> > print(cd_calendar(x,0))
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*> >
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*> > Thanks for your help
*

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Received on Sat Nov 5 10:26:23 2011

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