From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: John Cowan Newsgroups: gmane.lisp.guile.bugs Subject: bug#22034: time-utc->date shows bogus zone-dependent leap second Date: Thu, 25 Oct 2018 18:21:35 -0400 Message-ID: References: <20151127195146.GB28472@fysh.org> <87a7n847o5.fsf@netris.org> <87va5u8q7o.fsf@netris.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="0000000000004503c9057915071b" X-Trace: blaine.gmane.org 1540506008 32731 195.159.176.226 (25 Oct 2018 22:20:08 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 25 Oct 2018 22:20:08 +0000 (UTC) Cc: zefram@fysh.org, 22034@debbugs.gnu.org, 22034-done@debbugs.gnu.org To: Mark H Weaver Original-X-From: bug-guile-bounces+guile-bugs=m.gmane.org@gnu.org Fri Oct 26 00:20:03 2018 Return-path: Envelope-to: guile-bugs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gFnz1-0008PA-6Q for guile-bugs@m.gmane.org; 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charset="UTF-8" On Mon, Oct 22, 2018 at 2:12 AM Mark H Weaver wrote: Universal Time (UT) is not a measure of physical time, but rather is a > measure of the rotation angle of the Earth with respect to distant > quasars. A UT second is identified with a fixed amount of rotation of > the Earth, which equals 1/86400 of a mean solar day. That's why every > day has 86400 UT seconds. Quite right. Buit the whole point of UTC is that its seconds are not angles, but SI = TAI seconds. There are a variable number of these in a day, and a UTC clock will indeed report 23:59:60 at the end of a day with a leap second in it (and other civil-time clocks will similarly report :60 in whatever hour, according to their timezone offsets). See , which is a screenshot of https://time.gov displaying the last leap second. Now there are indeed exactly 86400 _Posix_ seconds in a day, which is achieved by giving two seconds the same label if it is a leap day. But that has nothing to do with either TAI or UTC. > UTC is kept within 0.9 seconds of UT1 (a > version of UT with certain corrections applied), so over long time > periods, with the leap seconds taken into account, UTC seconds are equal > to UT seconds. > No, in the long run UTC time is equal to UT1 time. That's not the same thing at all. -- John Cowan http://vrici.lojban.org/~cowan cowan@ccil.org I am expressing my opinion. When my honorable and gallant friend is called, he will express his opinion. This is the process which we call Debate. --Winston Churchill --0000000000004503c9057915071b Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On Mon, Oct 22, 2018 at 2:12 AM Mark H Weaver &= lt;mhw@netris.org> wrote:

Universal Time (UT) is not a measure of physical time, but rather is a measure of the rotation angle of the Earth with respect to distant
quasars.=C2=A0 A UT second is identified with a fixed amount of rotation of=
the Earth, which equals 1/86400 of a mean solar day.=C2=A0 That's why e= very
day has 86400 UT seconds.=C2=A0

Quite righ= t.=C2=A0 Buit the whole point of UTC is that its seconds are not angles,
but SI =3D TAI seconds.=C2=A0 There are a variable number of these = in a day, and
a UTC clock will indeed report 23:59:60 at the end = of a day with a leap
second in it (and other civil-time clocks wi= ll similarly report :60 in whatever
hour, according to their time= zone offsets).=C2=A0 See
which is = a screenshot of https://time.gov displayin= g the last leap second.

Now there are indeed exact= ly 86400 _Posix_ seconds in a day, which is
achieved by giving tw= o seconds the same label if it is a leap day.=C2=A0 But
that has = nothing to do with either TAI or UTC.
=C2=A0
UTC is kept within 0.9 seconds of UT1 (a=
version of UT with certain corrections applied), so over long time
periods, with the leap seconds taken into account, UTC seconds are equal to UT seconds.

No, in the long run UTC = time is equal to UT1 time.=C2=A0 That's not the same thing at all.

--=C2=A0
John Cowan=C2=A0 =C2=A0 =C2=A0= =C2=A0 =C2=A0 http://vrici.lojb= an.org/~cowan=C2=A0 =C2=A0 =C2=A0 =C2=A0 cowan@ccil.org
I am expressing my opinion.=C2=A0 When my = honorable and gallant friend is
called, he will express his opini= on.=C2=A0 This is the process which we
call Debate.=C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0--Winston Churchill<= /div>

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