Joe, Is there actually a free version available? That link you provided wants me to pay $220 for a PDF. It also asks my for some sort of personal login account for a HTML version. I'm not going there.
Please advise. Or better yet, post the PDF version here on LEAPSECS. /tvb ----- Original Message ----- From: Joseph M Gwinn To: Leap Second Discussion List Sent: Thursday, May 21, 2015 1:09 PM Subject: Re: [LEAPSECS] Look Before You Leap ? The Coming Leap Second and AWS | Hacker News "LEAPSECS" <leapsecs-boun...@leapsecond.com> wrote on 05/21/2015 08:02:09 AM: > From: "Eric R. Smith" <ersm...@hfx.eastlink.ca> > To: Leap Second Discussion List <leapsecs@leapsecond.com> > Date: 05/21/2015 08:01 AM > Subject: Re: [LEAPSECS] Look Before You Leap ? The Coming Leap > Second and AWS | Hacker News > Sent by: "LEAPSECS" <leapsecs-boun...@leapsecond.com> > > On 19/05/15 08:30 PM, Joseph M Gwinn wrote: > >> From: "Eric R. Smith" <ersm...@hfx.eastlink.ca> > >> To: Leap Second Discussion List <leapsecs@leapsecond.com> > >>> True UTC (with leap seconds) didn't cure a problem the committee cared > >>> about, and managed to cause problems they did care about. In short, > > POSIX > >>> systems have to be able to work in a cave, with no access to the sky or > >>> knowledge of astronomy. > >> > >> If POSIX time_t were actually a count of SI seconds elapsed since the > >> epoch, then a machine in a cave (with an accurate enough clock) could in > >> principle maintain correct timestamps. As it stands though, POSIX time_t > >> cannot be implemented without access to a UTC reference of some kind, > >> i.e. access to the sky. > > > > Well, while POSIX mentions SI seconds, the standard is careful to say that > > these seconds are not exactly SI seconds (because UNIX workstations can > > have pretty bad clocks). And the standard specifically disclaims being > > UTC, despite the appearance. Read the standard carefully. It is intended > > and designed to support isolated operation. > > I don't have the actual standard in front of me, but have seen claims > that POSIX time_t is defined (for years after 1970) to be: > > tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 + > (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 - > ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400 > > and that "each and every day shall be accounted for by exactly 86400 > seconds". Is this correct? Since the length of the day is not in fact > exactly 86400 SI seconds, it would follow that a POSIX compliant system > has to know how many days have elapsed since the epoch, i.e. it needs to > have some kind of access to the sky. Am I misunderstanding something? Yes. The actual standard. HTML access is free. <https://www2.opengroup.org/ogsys/jsp/publications/PublicationDetails.jsp?publicationid=11701> Look for Seconds Since the Epoch et al in the Rationale volume. The disclaim of UTC is explicit. There was a long thread on this on Time Nuts, where I published the details and links to the actual standard. Joe Gwinn ------------------------------------------------------------------------------ _______________________________________________ LEAPSECS mailing list LEAPSECS@leapsecond.com https://pairlist6.pair.net/mailman/listinfo/leapsecs
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