Re: December 2005 leap second on MSF, Rugby, England
In message: <[EMAIL PROTECTED]> "Joseph S. Myers" <[EMAIL PROTECTED]> writes: : The Linux kernel (with NTP synchronisation) duly syslogged : : Dec 31 23:59:59 digraph kernel: Clock: inserting leap second 23:59:60 UTC : : and Markus's program showed a transition from 1136073600.005623 to : 1136073599.013130, i.e. 23:59:59 was repeated (whereas a POSIX clock in : perfect synchronisation with UTC should appear to repeat 00:00:00, and a : kernel source code comment : : /* The timer interpolator will make time change gradually instead : * of an immediate jump by one second. : */ : : describes what would practically be a safer approach, if the code followed : the comment). ntp synced computers repeat the last second of the day. POSIX is just flat wrong here. Actually, POSIX is completely silent on what is to happen at the leap second to system time. Once can infer what might be the right behavior by working backwards from what mktime does for 23:59:60, but that's a weak inference for what the 'right' posix behavior is for the system time accross a leap second. POSIX simply does not have leap seconds in any meaningful way. It is as if they do not exist at all. There's no clarifications to the POSIX standard that say that 0:00:00 should be repeated at a leap second, at least that I've been able to find. If there is such an explicit clarification, I'd like to know about it. FreeBSD does the same thing (as do all kernels that use the ntp kernel stuff supplied with udel ntpd and successors). FreeBSD doesn't actually log the leap second via syslog, but maybe it should. Ideally, we'd switch to running computers with TAI and doing all the conversion on input/output of time. However, *THAT*'s definitely not POSIX. Warner
Re: December 2005 leap second on MSF, Rugby, England
On Sun, 1 Jan 2006, David Malone wrote: > I didn't have the facilities to record any phase information. I did > try recording BBC Radio 4, but they transmitted Big Ben rather than > pips ;-( Having found that problem with Radio 4 last leap second, I tried BBC World Service this time (having tested the night before that they broadcast the pips at midnight) but they also broadcast Big Ben for the New Year. Where does broadcast the pips at the New Year? The Linux kernel (with NTP synchronisation) duly syslogged Dec 31 23:59:59 digraph kernel: Clock: inserting leap second 23:59:60 UTC and Markus's program showed a transition from 1136073600.005623 to 1136073599.013130, i.e. 23:59:59 was repeated (whereas a POSIX clock in perfect synchronisation with UTC should appear to repeat 00:00:00, and a kernel source code comment /* The timer interpolator will make time change gradually instead * of an immediate jump by one second. */ describes what would practically be a safer approach, if the code followed the comment). I tried polling the plain text (not Java) clock on www.time.gov (via lynx -dump http://www.time.gov/timezone.cgi?UTC/s/0 | head -5), but around the time of the leap second that seemed heavily overloaded and taking much longer than a second to return results. However I alternated the results from that clock with local clock timestamps (which as above had had the leap second inserted by repeating 23:59:59), and a result from www.time.gov of Right now, the official U.S. time is: 00:00:05 Sunday, January 1, 2006 was immediately followed by a local timestamp of "Sun Jan 1 00:00:04 UTC 2006", suggesting that the www.time.gov text clock had not inserted the leap second at that point (or it has rounded the time to the next rather than the previous second boundary). I didn't think to log the HTTP header timestamps as well as the timestamp in the page text. -- Joseph S. Myers [EMAIL PROTECTED]
Re: December 2005 leap second on MSF, Rugby, England
> For those of you collecting leap second recordings, here is the 60 kHz > MSF time signal from Rugby, England, recorded in Cambridge, England: > http://www.cl.cam.ac.uk/~mgk25/time/lf-clocks/#msf-leapsec2005 I've some plots of the transitions in the Rugby signal recorded in Dublin (Ireland) at: http://www.maths.tcd.ie/~dwmalone/time/leap2005.html I didn't have the facilities to record any phase information. I did try recording BBC Radio 4, but they transmitted Big Ben rather than pips ;-( David.
Re: December 2005 leap second on MSF, Rugby, England
Keith Winstein wrote on 2006-01-01 11:52 UTC: > http://www.febo.com/time-freq/leapsecond-2005/ For those of you collecting leap second recordings, here is the 60 kHz MSF time signal from Rugby, England, recorded in Cambridge, England: http://www.cl.cam.ac.uk/~mgk25/time/lf-clocks/#msf-leapsec2005 Anyone got a GLONASS recording? Markus -- Markus Kuhn, Computer Laboratory, University of Cambridge http://www.cl.cam.ac.uk/~mgk25/ || CB3 0FD, Great Britain