Greg Dowd wrote: > I think it is the original rfc1305 (NTPv3) language that determined that > the bits only show up on the day of the event. While the actual > requirement is merely that they are set before 23:59 and cleared after > midnight, the supporting text is shown below. > > > "On the day prior to the insertion of a leap second the leap bits > (sys.leap) are set at the primary servers, presumably by manual means. > Subsequently, these bits show up at the local host and are passed to the > local-clock procedure. This causes the modulus of the time variable, > which is the length of the current day, to be increased or decreased by > one second as appropriate. Immediately following insertion the leap bits > are reset. Additional discussion on this issue can be found in Appendix > E." > >>From Appendix E > "The chronometry involved can be illustrated with the help of Figure 8, > which shows the details of seconds numbering just before, during and > after the last scheduled leap insertion at 23:59:59 on 31 December 1989. > Notice the NTP leap bits are set on the day prior to insertion, as > indicated by the <169>+<170> symbols on the figure. Since this makes the > day one second longer than usual, the NTP day rollover will not occur > until the end of the first occurrence of second 800. The UTC time > conversion routines must notice the apparent time and the leap bits and > handle the timescale conversions accordingly. Immediately after the leap > insertion both timescales resume ticking the seconds as if the leap had > never happened. The chronometric correspondence between the UTC and NTP > timescales continues, but NTP has forgotten about all past leap > insertions. In NTP chronometric determination of UTC time intervals > spanning leap seconds will thus be in error, unless the exact times of > insertion are known." > > When ntpv4 is standardized, the language changes to "leap at the end of > the current month". > > > -----Original Message----- > From: questions-bounces+gdowd=symmetricom....@lists.ntp.org > [mailto:questions-bounces+gdowd=symmetricom....@lists.ntp.org] On Behalf > Of David J Taylor > Sent: Monday, December 15, 2008 9:39 AM > To: questions@lists.ntp.org > Subject: Re: basic questions about the leapsecond > > David L. Mills wrote: >> Guys, >> >> See http://www.eecis.udel.edu/~mills/ntp/html/ntpd.html#leap for what >> actually is in the implementation. As visivle here, the Spectracom >> (GPS/WWVB) driver, ACTS telephone modem driver and WWV audio driver do >> correctly display leap information. The Meinberg GPS receiver, EndRun >> CDMA receiver and audio IRIG driver do not display leapsecond >> information. > [] >> Dave > > Dave, > > Thanks for that summary. My own GPS system using the Garmin GPS18 LVC > and > the official ntp code for FreeBSD also does /not/ show the leap second. > > Is this something fundamental to all GPS - in that they don't indicate > until nearer the end of the month? > > Thanks, > David
Did you READ the message you replied to? It seems quite clear to me! _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions