<div dir="ltr"><div><div><div><div><div>I don't have the text of ISO-8601 handy here, but my recollection<br></div>was that it is silent on what a time stamp without explicit time zone<br></div>information means.<br></div>Be that as it may, it does not explicitly allow for attaching time scale<br></div>labels to the date-time strings and hence pairing a bare string with<br></div><div>a time scale is a reasonable thing to do.<br></div><div>Pure use of JD or MJD is problematic if UTC is an allowed time<br></div><div>scale, since their values are ill-defined during days with leap seconds.<br></div><div>Besides, the date-time strings are nicely human readable.<br><br></div><div>Cheers,<br><br></div><div> - Arnold<br></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr">-------------------------------------------------------------------------------------------------------------<br>Arnold H. Rots Chandra X-ray Science Center<br>Smithsonian Astrophysical Observatory tel: +1 617 496 7701<br>60 Garden Street, MS 67 fax: +1 617 495 7356<br>Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank">arots@cfa.harvard.edu</a><br>USA <a href="http://hea-www.harvard.edu/~arots/" target="_blank">http://hea-www.harvard.edu/~arots/</a><br>--------------------------------------------------------------------------------------------------------------<br><br></div></div></div>
<br><div class="gmail_quote">On Tue, May 10, 2016 at 3:42 PM, Steve Allen <span dir="ltr"><<a href="mailto:sla@ucolick.org" target="_blank">sla@ucolick.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On Tue 2016-05-10T19:11:09 +0000, Paul Harrison hath writ:<br>
<span class="">> > FITS forbids the use of Z, for good reasons.<br>
><br>
> Then FITS should not even be mentioning ISO-8601 as not having the Z<br>
> in ISO-8601 means that the date time string should be interpreted as a<br>
> local time.<br>
<br>
</span>The FITS standard does not mention ISO 8601.<br>
<span class=""><br>
> I would suggest that to write any times in something like iso-8601<br>
> format when you want to express a time in a particular timescale<br>
> (other than UTC) is the act that should be banned, as it is highly<br>
> likely that your intentions will be misinterpreted<br>
<br>
</span>This ship has sailed, and yes, this is one of the icebergs out there.<br>
The standards bodies responsible for computer time representations<br>
explicitly disregarded advice to be able to handle precise time,<br>
so anyone trying to do that must diregard the standards.<br>
<div class="HOEnZb"><div class="h5"><br>
--<br>
Steve Allen <<a href="mailto:sla@ucolick.org">sla@ucolick.org</a>> WGS-84 (GPS)<br>
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</div></div></blockquote></div><br></div>