Chris,

That's a completely valid suggestion. We have to consider implications for backwards compatibility. Among other things, UDUNITS would need to change their convention, since CF follows UDUNITS in this matter, as with all other units. There's nothing that says we can't make changes. I was explaining the "is" as opposed to the "could be" with time units.

Grace and peace,

Jim


On 9/15/16 7:26 AM, Little, Chris wrote:
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.bar...@noaa.gov>
To: "cf-metadata@cgd.ucar.edu" <cf-metadata@cgd.ucar.edu>
Subject: [CF-metadata] nitpick in time axes example
Message-ID:
        <CALGmxE+S80kd1CnD-55btZZhz=vko-bbbps-bv2w2a-bu0w...@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



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