DALI 1.1 comments

[Arnold Rots]

I don't have the text of ISO-8601 handy here, but my recollection
was that it is silent on what a time stamp without explicit time zone
information means.
Be that as it may, it does not explicitly allow for attaching time scale
labels to the date-time strings and hence pairing a bare string with
a time scale is a reasonable thing to do.
Pure use of JD or MJD is problematic if UTC is an allowed time
scale, since their values are ill-defined during days with leap seconds.
Besides, the date-time strings are nicely human readable.

Cheers,

  - Arnold

-------------------------------------------------------------------------------------------------------------
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/
--------------------------------------------------------------------------------------------------------------


On Tue, May 10, 2016 at 3:42 PM, Steve Allen <sla at ucolick.org> wrote:

> On Tue 2016-05-10T19:11:09 +0000, Paul Harrison hath writ:
> > > FITS forbids the use of Z, for good reasons.
> >
> > Then FITS should not even be mentioning ISO-8601 as not having the Z
> > in ISO-8601 means that the date time string should be interpreted as a
> > local time.
>
> The FITS standard does not mention ISO 8601.
>
> > I would suggest that to write any times in something like iso-8601
> > format when you want to express a time in a particular timescale
> > (other than UTC) is the act that should be banned, as it is highly
> > likely that your intentions will be misinterpreted
>
> This ship has sailed, and yes, this is one of the icebergs out there.
> The standards bodies responsible for computer time representations
> explicitly disregarded advice to be able to handle precise time,
> so anyone trying to do that must diregard the standards.
>
> --
> 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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ivoa.net/pipermail/dal/attachments/20160510/5accfc88/attachment.html>