<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>