<div dir="ltr"><div>While "3...2...1...leap" was mentioned on the mailing list in 1998, support for rolling leap seconds goes all the way back to the 1.1, 1988-01-25 version of the leapseconds file (included below). Folks looking for documentation of "3...2...1...leap" in New York might focus on 1987 or, before that, 1972 through 1979. (My guess 1987.)</div><div><br></div><div> --ado</div><div><br></div><div># @(#)leapseconds 1.1<br><br># Allowance for leapseconds added to each timezone file.<br><br># The correction (+ or -) is made at the given time, so lines<br># will typically look like:<br># Leap YEAR MON DAY 23:59:60 + R/S<br># or<br># Leap YEAR MON DAY 23:59:59 - R/S<br><br># If the leapsecond is Rolling (R) the given time is local time<br># If the leapsecond is Stationary (S) the given time is GMT<br><br># Leap YEAR MONTH DAY HH:MM:SS CORR R/S<br>Leap 1972 Jun 30 23:59:60 + S<br>Leap 1972 Dec 31 23:59:60 + S<br>Leap 1973 Dec 31 23:59:60 + S<br>Leap 1974 Dec 31 23:59:60 + S<br>Leap 1975 Dec 31 23:59:60 + S<br>Leap 1976 Dec 31 23:59:60 + S<br>Leap 1977 Dec 31 23:59:60 + S<br>Leap 1978 Dec 31 23:59:60 + S<br>Leap 1979 Dec 31 23:59:60 + S<br>Leap 1981 Jun 30 23:59:60 + S<br>Leap 1982 Jun 30 23:59:60 + S<br>Leap 1983 Jun 30 23:59:60 + S<br>Leap 1985 Jun 30 23:59:60 + S<br>Leap 1987 Dec 31 23:59:60 + S<br></div><div><br> </div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Sep 13, 2021 at 3:57 AM Guy Harris <<a href="mailto:gharris@sonic.net">gharris@sonic.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Sep 13, 2021, at 12:18 AM, Paul Eggert via tz <<a href="mailto:tz@iana.org" target="_blank">tz@iana.org</a>> wrote:<br>
<br>
> Thanks for the background.<br>
<br>
You participated in the tz mailing list thread:<br>
<br>
<a href="http://mm.icann.org/pipermail/tz/1998-May/010164.html" rel="noreferrer" target="_blank">http://mm.icann.org/pipermail/tz/1998-May/010164.html</a><br>
<br>
in which he mentioned that back in 1998:<br>
<br>
<a href="http://mm.icann.org/pipermail/tz/1998-May/010159.html" rel="noreferrer" target="_blank">http://mm.icann.org/pipermail/tz/1998-May/010159.html</a><br>
<br>
(things I learned from a Web search today; no, I didn't remember that discussion, either).<br>
<br>
(And, on one of the topics you addressed in your message:<br>
<br>
> What Epoch do systems that use leap seconds use?<br>
> <br>
> In practice, such systems define 1972-01-01 00:00:00Z == (time_t) 63072000,<br>
> i.e. it's as if there were no leap seconds before 1972.<br>
<br>
Presumably systems that *don't* use leap seconds use the same definition.)<br>
<br>
</blockquote></div>