[DALI] timestamp format

[Arnold Rots]

Precisely, noting that astronomy has little use for time zones.
Both FITS and STC specifically state that they use a subset
of ISO 8601 - somewhat expanded in the WCS Time draft.

I meant "admissable" in a common sense way, with the FITS DATE
keyword as precedent - for cases that are not explicitly covered
by STC: times not related directly to the time coordinate of the
astronomical data presented, such as file creation times and
environmental data.

  - Arnold

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Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Wed, Nov 6, 2013 at 3:09 PM, Steve Allen <sla at ucolick.org> wrote:

> On Wed 2013-11-06T11:53:25 -0800, Patrick Dowler hath writ:
> > The choices are:
> >
> > - do not use the Z and refer to FITS and/or STC, in whch case the
> > document should not mention ISO8601 at all, or at least very
> > carefully)
> >
> > - use the Z and refer directly to ISO8601, which Dave argued is the
> > least surprising to the periphery and outside the IVOA but
> > incompatible with current practice in astronomy
> >
> > To Z or not to Z...
>
> The tzdata/tzcode (zoneinfo) remains constantly in flux and cannot be
> guaranteed to be correct on legacy systems.  For reasons like this we
> find that we must run some machines with the default timezone set to
> UTC, and on other machines the applications which need to avoid those
> issues explicitly set their timezone to UTC for the scope of the
> application.
>
> If I recall correctly the discussions leading to the FITS Y2K
> agreement explicitly wanted to prevent the complexities of
> timezone interpretation from entering the FITS standard.
> The first choice is the one that was made, specifically noting
> that it is only a subset of ISO8601.
>
> --
> Steve Allen                 <sla at ucolick.org>                WGS-84 (GPS)
> UCO/Lick Observatory--ISB   Natural Sciences II, Room 165    Lat  +36.99855
> 1156 High Street            Voice: +1 831 459 3046           Lng
> -122.06015
> Santa Cruz, CA 95064        http://www.ucolick.org/~sla/     Hgt +250 m
>
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