[CF-metadata] Temporal nitpicks. Was: CF-metadata Digest, Vol 161, Issue 3

From: Little, Chris <chris.little>
Date: Thu, 15 Sep 2016 11:26:46 +0000

Jim and Chris B,

I would like to weigh in here, please?

Adhering to UDUnits has merits, but once one adopts ISO8601-like notations, as there is no way of specifying otherwise, people assume it *is* ISO8601 and therefore a string without a time zone marker indicates local time (whatever that is - Solar? Mean Solar? Sidereal? National legal?)

There is work just starting in the OGC/ISO pipeline on how to indicate a non-Gregorian calendar using ISO8601 like notation, for the WKT communities.

Personally, I would advocate ISO8601 strict adherence, as most of the recommended best practices and profiles, such as RFC3339, are generally strict subsets of ISO 8601.

Chris


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Today's Topics:

   1. nitpick in time axes example (Chris Barker)
   2. Re: nitpick in time axes example (Jim Biard)


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Message: 1
Date: Wed, 14 Sep 2016 12:34:11 -0700
From: Chris Barker <chris.barker at noaa.gov>
To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
Subject: [CF-metadata] nitpick in time axes example
Message-ID:
        <CALGmxE+S80kd1CnD-55btZZhz=Vko-bbbpS-Bv2w2a-bu0wuvw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

I see in teh doc:

Example 4.4. Time axis

double time(time) ;
  time:long_name = "time" ;
  time:units = "days since 1990-1-1 0:0:0" ;

IIUC, ISO 8601 requires two digits for the time pieces [1], so that should
be:

"days since 1990-1-1 00:00:00"


The parser I use isn't picky about this, but maybe some are?

BTW, as it's an example, we should probably throw a time offset on there,
too:

"days since 1990-1-1 00:00:00Z"


or

"days since 1990-1-1 00:00:00+00:00"


[1] at least according to wikipedia:
https://en.wikipedia.org/wiki/ISO_8601#Times


-Chris

-- 
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception
Chris.Barker at noaa.gov
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Message: 2
Date: Wed, 14 Sep 2016 17:01:34 -0400
From: Jim Biard <jbiard at cicsnc.org>
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] nitpick in time axes example
Message-ID: <88f473d3-243e-0219-cfa8-ac975f5107b5 at cicsnc.org>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Chris,
CF has consistently maintained adherence to the UDUNITS definition for the reference time string, and that is different from ISO. (See CF Section 4.4
<http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html#time-coordinate>)
As stated at the top of the section, Z is not used in the case of UTC and there is a space before any time zone offset. Example 4.4 is written that way specifically to make it clear that single-digit numbers are legal.
Grace and peace,
Jim
On 9/14/16 3:34 PM, Chris Barker wrote:
> I see in teh doc:
>
> Example 4.4. Time axis
> double time(time) ;
>    time:long_name = "time" ;
>    time:units = "days since 1990-1-1 0:0:0" ; IIUC, ISO 8601 requires 
> two digits for the time pieces [1], so that should be:
>
> "days since 1990-1-1 00:00:00"
>
> The parser I use isn't picky about this, but maybe some are?
>
> BTW, as it's an example, we should probably throw a time offset on 
> there, too:
>
> "days since 1990-1-1 00:00:00Z"
>
> or
>
> "days since 1990-1-1 00:00:00+00:00"
>
> [1] at least according to wikipedia: 
> https://en.wikipedia.org/wiki/ISO_8601#Times
>
>
> -Chris
>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
> NOAA/NOS/OR&R            (206) 526-6959   voice
> 7600 Sand Point Way NE   (206) 526-6329   fax
> Seattle, WA  98115       (206) 526-6317   main reception
>
> Chris.Barker at noaa.gov <mailto:Chris.Barker at noaa.gov>
>
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
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Received on Thu Sep 15 2016 - 05:26:46 BST