Not my issue, but the last day of the 20th century is technically December 31, 2000. I wish it weren't. When this controversy passed in 1701, Isaac Newton is quoted has having rejoiced that "the issue was finally behind us".
Also, I would add November 18, 1858 as the first day in the Modified Julian Date system, although MJD was not introduced until much later. Apologies if this email comes out of sequence - I am only signed up for daily batches. -----Original Message----- From: leapsecs-boun...@leapsecond.com [mailto:leapsecs-boun...@leapsecond.com] On Behalf Of leapsecs-requ...@leapsecond.com Sent: Tuesday, January 14, 2014 5:34 AM To: leapsecs@leapsecond.com Subject: LEAPSECS Digest, Vol 88, Issue 31 Send LEAPSECS mailing list submissions to leapsecs@leapsecond.com To subscribe or unsubscribe via the World Wide Web, visit http://six.pairlist.net/mailman/listinfo/leapsecs or, via email, send a message with subject or body 'help' to leapsecs-requ...@leapsecond.com You can reach the person managing the list at leapsecs-ow...@leapsecond.com When replying, please edit your Subject line so it is more specific than "Re: Contents of LEAPSECS digest..." Today's Topics: 1. Re: presentations from AAS Future of Time sessions (Michael Deckers) 2. Re: presentations from AAS Future of Time sessions (Brooks Harris) 3. Re: presentations from AAS Future of Time sessions (John Hawkinson) 4. Re: presentations from AAS Future of Time sessions (Rob Seaman) 5. Re: presentations from AAS Future of Time sessions (Zefram) ---------------------------------------------------------------------- Message: 1 Date: Mon, 13 Jan 2014 17:29:00 +0000 From: Michael Deckers <michael.deck...@yahoo.com> Subject: Re: [LEAPSECS] presentations from AAS Future of Time sessions To: Leap Second Discussion List <leapsecs@leapsecond.com> Message-ID: <52d4225c.2050...@yahoo.com> Content-Type: text/plain; charset=UTF-8; format=flowed On 2014-01-12 03:28, Brooks Harris quoted from RFC 5905: > Then, and very importantly, Figure 4: Interesting Historic NTP Dates > states the relationship to "First day UNIX" - > > +-------------+------------+-----+---------------+------------------+ > | Date | MJD | NTP | NTP Timestamp | Epoch | > | | | Era | Era Offset | | > +-------------+------------+-----+---------------+------------------+ > | 1 Jan -4712 | -2,400,001 | -49 | 1,795,583,104 | 1st day Julian | > | 1 Jan -1 | -679,306 | -14 | 139,775,744 | 2 BCE | > | 1 Jan 0 | -678,491 | -14 | 171,311,744 | 1 BCE | > | 1 Jan 1 | -678,575 | -14 | 202,939,144 | 1 CE | > | 4 Oct 1582 | -100,851 | -3 | 2,873,647,488 | Last day Julian | > | 15 Oct 1582 | -100,840 | -3 | 2,874,597,888 | First day | > | | | | | Gregorian | > | 31 Dec 1899 | 15019 | -1 | 4,294,880,896 | Last day NTP Era | > | | | | | -1 | > | 1 Jan 1900 | 15020 | 0 | 0 | First day NTP | > | | | | | Era 0 | > | 1 Jan 1970 | 40,587 | 0 | 2,208,988,800 | First day UNIX | > | 1 Jan 1972 | 41,317 | 0 | 2,272,060,800 | First day UTC | > | 31 Dec 1999 | 51,543 | 0 | 3,155,587,200 | Last day 20th | > | | | | | Century | > | 8 Feb 2036 | 64,731 | 1 | 63,104 | First day NTP | > | | | | | Era 1 | > +-------------+------------+-----+---------------+------------------+ Please note that this table has to be read with caution. Besides the typo -678,491 for -678,941, one has to realize that "1 Jan -4712" is meant as a date in the Julian calendar, but all the other dates in column 1 must be taken as Gregorian calendar dates, even those before 1582-10-15 -- else the entries in columns 2,3,4 become incorrect. And this makes the entry in column 5 for the date 1582-10-04 incorrect. Michael Deckers. ------------------------------ Message: 2 Date: Mon, 13 Jan 2014 10:37:28 -0800 From: Brooks Harris <bro...@edlmax.com> Subject: Re: [LEAPSECS] presentations from AAS Future of Time sessions To: leapsecs@leapsecond.com Message-ID: <52d43268.70...@edlmax.com> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" On 2014-01-13 09:29 AM, Michael Deckers wrote: > > On 2014-01-12 03:28, Brooks Harris quoted from RFC 5905: > >> Then, and very importantly, Figure 4: Interesting Historic NTP Dates >> states the relationship to "First day UNIX" - >> >> +-------------+------------+-----+---------------+------------------+ >> | Date | MJD | NTP | NTP Timestamp | Epoch | >> | | | Era | Era Offset | | >> +-------------+------------+-----+---------------+------------------+ >> | 1 Jan -4712 | -2,400,001 | -49 | 1,795,583,104 | 1st day Julian | >> | 1 Jan -1 | -679,306 | -14 | 139,775,744 | 2 BCE | >> | 1 Jan 0 | -678,491 | -14 | 171,311,744 | 1 BCE | >> | 1 Jan 1 | -678,575 | -14 | 202,939,144 | 1 CE | >> | 4 Oct 1582 | -100,851 | -3 | 2,873,647,488 | Last day Julian | >> | 15 Oct 1582 | -100,840 | -3 | 2,874,597,888 | First day | >> | | | | | Gregorian | >> | 31 Dec 1899 | 15019 | -1 | 4,294,880,896 | Last day NTP Era | >> | | | | | -1 | >> | 1 Jan 1900 | 15020 | 0 | 0 | First day NTP | >> | | | | | Era 0 | >> | 1 Jan 1970 | 40,587 | 0 | 2,208,988,800 | First day UNIX | >> | 1 Jan 1972 | 41,317 | 0 | 2,272,060,800 | First day UTC | >> | 31 Dec 1999 | 51,543 | 0 | 3,155,587,200 | Last day 20th | >> | | | | | Century | >> | 8 Feb 2036 | 64,731 | 1 | 63,104 | First day NTP | >> | | | | | Era 1 | >> >> +-------------+------------+-----+---------------+------------------+ > > Please note that this table has to be read with caution. > > Besides the typo -678,491 for -678,941, one has to realize that > "1 Jan -4712" is meant as a date in the Julian calendar, but > all the other dates in column 1 must be taken as Gregorian calendar > dates, even those before 1582-10-15 -- else the entries in > columns 2,3,4 become incorrect. And this makes the entry > in column 5 for the date 1582-10-04 incorrect. > > Michael Deckers. > > _______________________________________________ > LEAPSECS mailing list > LEAPSECS@leapsecond.com > http://six.pairlist.net/mailman/listinfo/leapsecs > > Oh dear! I had "worked" the numbers after 1900 to confirm (a pain to do), and was suggesting this table as the normative the link between 1 Jan 1970-First day UNIX and 1 Jan 1972-First day UTC. I had not bothered to verify the earlier values, but its important. I suppose Mills did this table. I'm sympathectic to how tricky it is to do and confirm these values. It also highlights why due-process is important - the better to catch mistakes like that. -Brooks -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://six.pairlist.net/pipermail/leapsecs/attachments/20140113/3adecd67/attachment-0001.html> ------------------------------ Message: 3 Date: Mon, 13 Jan 2014 15:54:37 -0500 From: John Hawkinson <jh...@mit.edu> Subject: Re: [LEAPSECS] presentations from AAS Future of Time sessions To: Leap Second Discussion List <leapsecs@leapsecond.com> Message-ID: <20140113205437.gt12...@athena.dialup.mit.edu> Content-Type: text/plain; charset=us-ascii Poul-Henning Kamp <p...@phk.freebsd.dk> wrote on Mon, 13 Jan 2014 at 16:03:28 +0000 in <86897.1389629...@critter.freebsd.dk>: > I don't think he told me exactly what representation they used before > time_t became 32bit*seconds, but prior to that, the wrap-around of > timestamps was prevented only by the kernel crashes. I have no point, I just want to say: "Sun Patch 102982-02, bug #4032974 system hangs when lbolt wraps around." may be familiar to some people on this list. How history repeats itself. In other news, the count of the number of times in this thread folks have said "Universal Time Coordinated" instead of "Coordinated Universal Time" is higher than I would expect. (Coordinated Universal Time is the proper expansion of UTC, for international compromise reasons). I feel like this is similar to the times people say "GMT" when they mean "UTC," and possibly for similar reasons. --jh...@mit.edu John Hawkinson ------------------------------ Message: 4 Date: Mon, 13 Jan 2014 14:49:35 -0700 From: Rob Seaman <sea...@noao.edu> Subject: Re: [LEAPSECS] presentations from AAS Future of Time sessions To: Leap Second Discussion List <leapsecs@leapsecond.com> Message-ID: <4ae135ed-c55e-4161-a2e5-ca6cd9063...@noao.edu> Content-Type: text/plain; charset=us-ascii On Jan 13, 2014, at 1:54 PM, John Hawkinson <jh...@mit.edu> wrote: > In other news, the count of the number of times in this thread folks > have said "Universal Time Coordinated" instead of "Coordinated > Universal Time" is higher than I would expect. (Coordinated Universal > Time is the proper expansion of UTC, for international compromise > reasons). I feel like this is similar to the times people say "GMT" > when they mean "UTC," and possibly for similar reasons. For diplomatic and legal usage, see also: http://www.cacr.caltech.edu/futureofutc/preprints/files/8_AAS%2013-505_Gabor.pdf http://www.cacr.caltech.edu/futureofutc/preprints/files/9_AAS%2013-505discussion.pdf and: http://www.cacr.caltech.edu/futureofutc/2011/preprints/04_AAS_11-662_Seago.pdf http://www.cacr.caltech.edu/futureofutc/2011/preprints/05_AAS_11-662_discuss_2.pdf Rob ------------------------------ Message: 5 Date: Tue, 14 Jan 2014 10:33:34 +0000 From: Zefram <zef...@fysh.org> Subject: Re: [LEAPSECS] presentations from AAS Future of Time sessions To: Leap Second Discussion List <leapsecs@leapsecond.com> Message-ID: <20140114103334.gv21...@fysh.org> Content-Type: text/plain; charset=us-ascii Poul-Henning Kamp wrote: >They chose UTC because they meant UTC. ... >The reason why they didn't cater to leap-seconds ? > >They hadn't heard about them at the time. It's dubious to say that they meant UTC if they weren't aware of leap seconds. As that's the defining feature of UTC (well, nearly, modulo the rubber-seconds era), in theory anyone who means UTC must mean the time scale with leap seconds. This is part of the advice that I commonly dispense about time scales: "if you don't mean leap seconds then don't say `UTC'". It appears that the POSIX people made the same mistake as a lot of people who have heard the term "UTC" but don't really know what it means. They want to refer to the consensus basis of civil time, observe that the technical people call it "UTC", and come away with the impression that that's just the new name for GMT. It is the inevitable fate of technical terminology, to become diluted by popular misuse. This is particularly noticeable on Wikipedia, where the page titled "Coordinated Universal Time" is mainly about the base time zone, and the real description of UTC is relegated to a separate page titled "leap second". -zefram ------------------------------ _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs End of LEAPSECS Digest, Vol 88, Issue 31 **************************************** _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com http://six.pairlist.net/mailman/listinfo/leapsecs
