Hi Nan,
We've been using 8601 in SeaDataNet for a while, mainly - but not (unfortunately in my view) exclusively for metadata. As soon as 8601 appeared, the first thing we did was make a clear statement that within SeaDataNet any 8601 string that did not include an explicit time zone would be assumed to be UT. Further, the only valid 8601 explicit time zone in SeaDataNet is 'Z'.
This is what I would describe as a necessary straitjacket. If CF embraces 8601 I totally agree with Nan that following the same course as SeaDataNet would be a shrewd move.
Cheers, Roy.
________________________________
From: CF-metadata [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Nan Galbraith [ngalbraith at whoi.edu]
Sent: 19 March 2013 19:08
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] New standard name: datetime_iso8601
There seems to be surprisingly broad support for this idea, so I've been
re-reading the thread, looking for a reasonable use case. I can't say that
I've found any description of why we actually need this - am I missing
something?
Anyway, going back to Aleksandar's original (slightly amended) proposal of
Jan 11 just for a moment... I'd like to clarify one detail. As far as I know,
ISO 8601 calls for the default time zone to be local, not UTC.
If we're going to add this option to CF, we should *at least* require the time
zone to be specified. Allowing a default, and having that default NOT align
with ISO, is just too much to ask. Either we're implementing ISO, or not -
changing the default meaning of the time zone would truly mislead our
imaginary post-apocalyptic researchers - and I know how much we all
worry about them.
>From Wikipedia (my only available ISO documentation):
Time zones in ISO 8601 are represented as local time (with the location
unspecified), as UTC, or as an offset from UTC.
If no UTC relation information is given with a time representation, the
time is assumed to be in local time.
Cheers - Nan
On 1/11/13 12:00 PM, Aleksandar Jelenak - NOAA Affiliate wrote:
Dear All:
Here's the modified proposal for the datetime_iso8601 standard name:
standard_name: datetime_iso8601
Units: N/A
String representing date-time information according to the ISO
8601:2004(E) standard. Variables with this standard name cannot serve
as coordinate variables. Date-time information is in the Gregorian
calendar. For dates preceding the Gregorian calendar the date-time
information is in the proleptic Gregorian calendar. Possible date-time
string forms are:
<datetime> = <date> "T" <time> <timezone> ;
<date> = YYYY "-" MM "-" DD | YYYY "-" DDD ;
<time> = hh | hh ":" mm | hh ":" mm ":" ss | hh ":" mm ":" ss "." S
| hh ":" mm ":" ss "," S ;
<timezone> = "" | "Z" | "+" hh | "+" hh ":" mm | "-" hh | "-" hh ":" mm
Where:
* "YYYY" is a four-digit year (0000-9999).
* "MM" is a two-digit month of the year (01-12).
* "DD" is a two-digit day of the month (01-31).
* "DDD" is a three-digit ordinal day of the year (001-366).
* "hh" is a two-digit hour (00-23).
* "mm" is a two-digit minute (00-59)
* "ss" is a two-digit second (00-60).
* "S" is one or more digits representing a decimal fraction of the
second.
* The value of any designator when not specified is zero.
* If <timezone> is ommitted the default value is "Z".
--
*******************************************************
* Nan Galbraith Information Systems Specialist *
* Upper Ocean Processes Group Mail Stop 29 *
* Woods Hole Oceanographic Institution *
* Woods Hole, MA 02543 (508) 289-2444 *
*******************************************************
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