<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> Poul-Henning Kamp wrote:</span></font></div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font><blockquote type="cite"><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Rob Seaman writes:<br><br></span></font><blockquote type="cite"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">3) My own point of view focuses on the requirements for "wall <br></span></font></blockquote><blockquote type="cite"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">clocks". Civil timekeeping has (heretofore) been mean solar time <br></span></font></blockquote><blockquote type="cite"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">[...]<br></span></font></blockquote><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br>You mean "has been within a couple of hours of mean solar time" ?</span></font></div></blockquote><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">No. I mean "mean solar time". As explained, for instance, in 2005 (I could go back farther):</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676.html">http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676.html</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">and</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://www.febo.com/pipermail/time-nuts/2005-July/018991.html">http://www.febo.com/pipermail/time-nuts/2005-July/018991.html</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">and in 2006:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00954.html">http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00954.html</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">and in 2007:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://catless.ncl.ac.uk/Risks/24.79.html#subj3">http://catless.ncl.ac.uk/Risks/24.79.html#subj3</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">and in 2008:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://six.pairlist.net/pipermail/leapsecs/2008-January/000184.html">http://six.pairlist.net/pipermail/leapsecs/2008-January/000184.html</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Searching on these various lists (or via google or in my mail folders) hasn't uncovered a message I remember sending to one of the lists that addressed the question even more explicitly, but the plots from that message are in the first link above. In any event, I've attempted to answer this question over and over and it keeps popping up. My apologies for failing to find the words to make the point clear.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Briefly: Apparent solar time is a red herring (<span class="Apple-style-span" style="font-size: 14px; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px; "><a href="http://www.nizkor.org/features/fallacies/red-herring.html)">http://www.nizkor.org/features/fallacies/red-herring.html)</a>.</span></font><span class="Apple-style-span" style="font-size: 13px; "> Mean solar time is simply sidereal time (the "real" length of day on Earth) offset by about 4 minutes to make up for the Earth lapping the Sun once a year. The issue is the stability of the rate, not some imagined average over lots of separate measurements of the Sun's apparent position in the sky. After all, we circle the Sun, not the other way around. Local time is an offset from mean solar time, not the other way around.</span></span></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">The first plot in the first link:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><span class="Apple-style-span" style="font-size: 14px; "><div><span class="Apple-tab-span" style="white-space: pre; "><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px; "> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px; "><a href="http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676/daylength.pdf">http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676/daylength.pdf</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div></span></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">shows that the sidereal rate (adjusted for one lapped day per year) is quite stable, even when the shape of the Earth's orbit and the inclination of its axis are accommodated. (I'll keep looking for that message, it discussed all this.) Rather, the issue is confused by the sundial corrections shown in the second plot, grandly named the "equation of time". The EOT is nothing special, just the integral of the modest annual LOD excursions. Static timezone offsets and periodic DST zero point adjustments are similarly beside the point.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Even briefer: The real length of the day on the planet earth for human purposes is the mean solar day. Introducing a secular trend into this is a poor idea with a limited lifespan. Eventually the embargoed leap seconds (or equivalent) will have to be released, else it is the definition of "day" that will be broken. Any viable proposal has to include some plan for what happens then.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font><blockquote type="cite"><div><blockquote type="cite"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">4) The ITU proposal is basically an assertion that people don't care <br></span></font></blockquote><blockquote type="cite"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">about mean solar time.<br></span></font></blockquote><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br>The fact that the majority of the earths population use a legal time<br>that is more than 15 minutes different from mean solaer time, would<br>seem to support the ITU in this.</span></font></div></blockquote><div><br></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px; ">Local time is not the issue, has never been the issue, has nothing to do with the issue.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px; ">The issue is stabilizing the daily rate of the underlying "universal" time scale.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><blockquote type="cite"><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Have you or others provided any documentation for the opposite claim ?<br></span></font></div></blockquote><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Over and over and over.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">Here's another go: As you say, it is likely that most people rely on local standard time that is more than 15 minutes different from local mean solar time at their location. In addition, their local apparent solar time has excursions from their local mean time of around 15 minutes in amplitude (although most of the year, they will be closer than this). In addition, their local government may institute DST adjustments of an hour or more. The citizens may also be jet lagged, for that matter.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">However: Everybody everywhere, throughout history, has observed a day whose LENGTH throughout the year is within +/- 30 SI seconds of the mean solar day length:</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-tab-span" style="white-space:pre"><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"> </span></font></span><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><a href="http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676/daylength.pdf">http://www.mail-archive.com/leapsecs@rom.usno.navy.mil/msg00676/daylength.pdf</a></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;">The ITU is attempting to tilt the baseline of this plot. (Or rather, remove the controls that periodically accommodate the natural tilt.) Whether or not you believe this is an acceptable kludge, it most definitely is a kludge. Such a secular trend cannot accumulate forever.</span></font></div><div><font class="Apple-style-span" size="3"><span class="Apple-style-span" style="font-size: 13px;"><br></span></font></div><div><span class="Apple-style-span" style="font-size: 13px; ">Rob</span></div></body></html>