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<div dir="ltr" spellcheck="false" style="">Hello,</div>
<div dir="ltr" spellcheck="false" style=""> The current integer leap second system did not exist before 1972. There were a number of fractional-second adjustments and there were also frequency adjustments starting in the 1950s, when the length of the cesium
second was defined. The final time adjustment at the start of 1972 was intended to incorporate the integral of the previous frequency steps, since the frequency of UTC was set equal to the SI second at that time. It is quite challenging to compute time intervals
in the pre-1972 era.</div>
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<div dir="ltr" spellcheck="false" style="">Different timing laboratories had slightly different values for this final time step. The goal was to bring all of the real-time realizations of UTC to the same time.</div>
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<div dir="ltr" spellcheck="false" style="">Judah Levine<br>
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On: 09 November 2018 22:29, "Steve Allen" <<a href="mailto:sla@ucolick.org">sla@ucolick.org</a>> wrote:<br>
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<div class="PlainText">On Fri 2018-11-09T22:04:35-0700 Paul Gilmartin via tz hath writ:<br>
> Subject: [tz] Was there a 1971-12-31 23:59:60?<br>
<br>
No.<br>
<br>
There was a step of 0.107758 seconds in UTC(BIH) at 1972-01-01.<br>
This was the final sub-second step in coordinated broadcast time signals.<br>
<br>
for the step that was applied to UTC(USNO) see<br>
Time Service Announcement series 14 number 8 (1971-10-08)<br>
at<br>
<a href="https://na01.safelinks.protection.outlook.com/?url=https:%2F%2Fwww.ucolick.org%2F~sla%2Fleapsecs%2Fleapincept.html&data=02%7C01%7CJudah.Levine%40nist.gov%7Cbe5617bc38fd469863b508d646cd8a53%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636774245940004523&sdata=Ju3hU%2FPYznG15Udu9qFK4yfC9%2FJDJDfRXN6igfWXq5k%3D&reserved=0" target="_BLANK">https://na01.safelinks.protection.outlook.com/?url=https:%2F%2Fwww.ucolick.org%2F~sla%2Fleapsecs%2Fleapincept.html&data=02%7C01%7CJudah.Levine%40nist.gov%7Cbe5617bc38fd469863b508d646cd8a53%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636774245940004523&sdata=Ju3hU%2FPYznG15Udu9qFK4yfC9%2FJDJDfRXN6igfWXq5k%3D&reserved=0</a><br>
<br>
--<br>
Steve Allen <<a href="mailto:sla@ucolick.org">sla@ucolick.org</a>> WGS-84 (GPS)<br>
UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855<br>
1156 High Street Voice: +1 831 459 3046 &nb</div>
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