<div dir="auto">And this is precisely the part of ISO 8601 that does not make sense in astronomy: the exclusive choice between a time zone and UTC. Hence, the community has accepted a limited version of the ISO 8601 value string which is required to be associated with a specification of the time coordinate frame (including a time scale). <div dir="auto">See FITS WCS Paper IV.</div><div dir="auto"><br></div><div dir="auto">Cheers, </div><div dir="auto"><br></div><div dir="auto"> - Arnold </div></div><br><div class="gmail_quote"><div dir="ltr">On Thu, Jan 10, 2019, 17:11 Graham, Matthew J. <<a href="mailto:mjg@caltech.edu">mjg@caltech.edu</a> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">The ISO 8601 spec is very clear: "The  zone  designator   is   empty  if   use   is   made  of   local  time  in   accordance   with  4.2.2.2 through 4.2.2.4,    it   is   the   UTC   designator   [Z]   if use is   made  of   UTC   of   day   in   accordance   with  4.2.4  and   it   is   the   difference-component  if   use   is   made  of   local  time  and   the   difference   from  UTC   in   accordance   with 4.2.5.2.†If you don’t use the zone designator as in the standard then it’s not ISO 8601.<br>
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— Matthew</blockquote></div>