On Thu, Sep 22, 2016 at 2:11 PM, Aaron Sweeney - NOAA Affiliate < aaron.swee...@noaa.gov> wrote:
> In case you and others are not already aware the Internet Engineering > Task Force (IETF) RFC 3339: "Date and Time on the Internet: Timestamps," > circa 2002, (see https://www.ietf.org/rfc/rfc3339.txt, especially > Appendix A) requires the "T." This spec adheres to ISO 8601, but is more > restrictive. Most date/time libraries can handle this fine. > good to know, but I don't know if there's any way to know how well supported it is across the board in CF readers :-( -CHB > Cordially, > Aaron > > On Thu, Sep 22, 2016 at 2:54 PM, <cf-metadata-requ...@cgd.ucar.edu> wrote: > >> Send CF-metadata mailing list submissions to >> cf-metadata@cgd.ucar.edu >> >> To subscribe or unsubscribe via the World Wide Web, visit >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> or, via email, send a message with subject or body 'help' to >> cf-metadata-requ...@cgd.ucar.edu >> >> You can reach the person managing the list at >> cf-metadata-ow...@cgd.ucar.edu >> >> When replying, please edit your Subject line so it is more specific >> than "Re: Contents of CF-metadata digest..." >> >> >> Today's Topics: >> >> 1. Re: Temporal nitpicks. Was: CF-metadata Digest, Vol 161, >> Issue 3 (Chris Barker) >> >> >> ---------------------------------------------------------------------- >> >> Message: 1 >> Date: Thu, 22 Sep 2016 13:54:04 -0700 >> From: Chris Barker <chris.bar...@noaa.gov> >> To: Jim Biard <jbi...@cicsnc.org> >> Cc: "cf-metadata@cgd.ucar.edu" <cf-metadata@cgd.ucar.edu> >> Subject: Re: [CF-metadata] Temporal nitpicks. Was: CF-metadata Digest, >> Vol 161, Issue 3 >> Message-ID: >> <CALGmxEJoWkZ=-_AwA-d=AH-x9t1o+u9AgaMHtMKSXRkaaEpgwg@mail. >> gmail.com> >> Content-Type: text/plain; charset="utf-8" >> >> On Thu, Sep 22, 2016 at 12:06 PM, Jim Biard <jbi...@cicsnc.org> wrote: >> >> > So I went and dug into the source code for UDUNITS and UDUNITS-2. Both >> > versions of UDUNITS allow a wide variety of epoch date/time formulations >> > with and without space delimiters between just about any of the >> components, >> > with and without leading zeros, with and without a 'T' between the date >> and >> > the time, and allowing 'UTC', 'GMT', or 'Z' (in addition to the >> 'classical' >> > YYYY-MM-DD hh:mm:ss[.sss] [-]h:mm form). >> > >> > >> Thanks! so UDUNITS is quite flexible -- make this easier :-) >> >> > So on one level this seems like a case for modifying the documentation >> > without a formal change to the convention. Except... >> > >> > The CF time convention is out there already with the pretty well >> > understood classical form that I mentioned above. >> > >> Isn't the "classical" form ISO8601 without the "T" ? >> >> > Software written to that form could very well break if a different form >> is >> > used. >> > >> well, the spec says UDUnits, so it's up to the software to fix itself :-) >> IN any case, I know I"ve seen files that claim to be CF compliant both >> with >> and without the "T" -- and, in fact, we had to update the python lib a >> couple years ago to accommodate the "T". But if we are sure that the no T >> version is the most common, then whe can make that the official >> recommendation -- it does seem to be ISO compliant a swell. >> >> In addition, there is an issue that connects with all of this that I've >> > been horribly slow to write a ticket on. It has to do with time systems >> > other than UTC, such as native GPS and TAI, that don't have leap >> seconds. >> > >> yeah, that's a mess, but a distinct issue, yes? >> >> At the very minimum, we need to make it very clear that times without >> > offsets or designators ARE NOT local times. This is baked deeply enough >> > into CF and existing data sets that I don't see any clean way to go with >> > ISO8061. >> > >> This is in the docs now: >> >> *Note: if the time zone is omitted the default is UTC, and if both time >> and >> time zone are omitted the default is 00:00:00 UTC.* >> >> Which is unfortunate. But it's been there "forever", yes? It does mean >> that >> there is no way in CF to specify local time, but that may be a good thing. >> "local time" is a really poorly defined concept. I don't have the official >> ISO docs, but the wikipedia page doesn't define it. >> >> In other contexts (at least the Python datetime world) the concept "naive >> time" is used. what this means is that you have no idea what time zone it >> is, but it behaves as UTC (i.e. no DST). It's up to the app to know what >> time zone it is dealing with. I think that's what an ISO8601 string with >> no >> offset really is. >> >> But CF says it's UTC, so it's UTC. >> >> But we don't have to actually recommend that anyone use that, or show it >> in >> any examples. >> >> Are we converging on ISO8601 without the "T", and always with an offset or >> "Z" as the recommended way to express datetimes in CF? >> >> -CHB >> >> >> >> >> > This leads me to think that any change should be considered a change to >> > the time convention, not just a document edit. >> > >> > Grace and peace, >> > >> > Jim >> > On 9/22/16 12:23 PM, Steve Emmerson wrote: >> > >> > On Thu, Sep 22, 2016 at 9:45 AM, Chris Barker <chris.bar...@noaa.gov> >> > wrote: >> > >> >> I think UDUnits does not use a T but maybe it will accept it. >> >> >> > >> > UDUNITS accepts the "T" and can print it. >> > >> > Regards, >> > Steve Emmerson >> > >> > >> > _______________________________________________ >> > CF-metadata mailing listcf-metad...@cgd.ucar.eduhttp:// >> mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> > >> > >> > -- >> > [image: CICS-NC] <http://www.cicsnc.org/> Visit us on >> > Facebook <http://www.facebook.com/cicsnc> *Jim Biard* >> > *Research Scholar* >> > Cooperative Institute for Climate and Satellites NC <http://cicsnc.org/ >> > >> > North Carolina State University <http://ncsu.edu/> >> > NOAA National Centers for Environmental Information >> > <http://ncdc.noaa.gov/> >> > *formerly NOAA?s National Climatic Data Center* >> > 151 Patton Ave, Asheville, NC 28801 >> > e: jbi...@cicsnc.org >> > o: +1 828 271 4900 >> > >> > *Connect with us on Facebook for climate >> > <https://www.facebook.com/NOAANCEIclimate> and ocean and geophysics >> > <https://www.facebook.com/NOAANCEIoceangeo> information, and follow us >> on >> > Twitter at @NOAANCEIclimate <https://twitter.com/NOAANCEIclimate> and >> > @NOAANCEIocngeo <https://twitter.com/NOAANCEIocngeo>. * >> > >> > _______________________________________________ >> > CF-metadata mailing list >> > CF-metadata@cgd.ucar.edu >> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> > >> > >> >> >> -- >> >> 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.bar...@noaa.gov >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachmen >> ts/20160922/1c02f6bb/attachment.html> >> -------------- next part -------------- >> A non-text attachment was scrubbed... >> Name: CicsLogoTiny.png >> Type: image/png >> Size: 15784 bytes >> Desc: not available >> URL: <http://mailman.cgd.ucar.edu/pipermail/cf-metadata/attachmen >> ts/20160922/1c02f6bb/attachment.png> >> >> ------------------------------ >> >> Subject: Digest Footer >> >> _______________________________________________ >> CF-metadata mailing list >> CF-metadata@cgd.ucar.edu >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >> >> >> ------------------------------ >> >> End of CF-metadata Digest, Vol 161, Issue 12 >> ******************************************** >> > > > > -- > Aaron D. Sweeney, Ph. D. > Water Level Data Manager > > Cooperative Institute for Research in Environmental Sciences (CIRES) > University of Colorado at Boulder > and > NOAA National Centers for Environmental Information > *formerly NOAA's National Geophysical Data Center* > 325 Broadway, E/NE42 > Boulder, CO 80305-3328 > > Phone: 303-497-4797, Fax: 303-497-6513 > > DISCLAIMER: The contents of this message are mine personally and do not > necessarily reflect any position of NOAA. > > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > -- 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.bar...@noaa.gov
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