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SubjectRe: updating the RTC automagically
On Fri, 19 Nov 1999, Arjan van de Ven wrote:

> In article <19991119113906.B10503@win.tue.nl> you wrote:
>
> > But the timezone offset is already maintained in the kernel.
> > (The way it is done is broken, but that is a different matter.)
> > And hwclock tells the kernel about the present timezone.
>
> Ok. As UTC <-> Unix time isn't _that_ difficult (kHTTPd needs to do just
> that), I think the argument "Doing time-calculations in the kernel is
> impossible" doesn't hold. This is with the possible exception of DST, but I
> think hwclock can be persuaded to inform the kernel about that as well.
>
> [This doesn't mean I think the kernel should set the RTC, hwclock suits my
> needs perfectly]
>
> Greetings,
> Arjan van de Ven

The time-keeper (32kHz temperature-compenstated piezoelectric resonator)
in the RTC is much more stable than the CPU clock, which in recent
boards isn't even a quartz crystal, it's a cheap barium titanate
"Ceramic resonator".

I don't think the you should set the RTC from the kernel except during
the following once-a-day crond script.

rdate time-a.timefreq.bldrdoc.gov # Set time to NIST
clock -w # Set RTC to your time

This will keep your RTC within a second for all time. FYI, most
kernels show the stability per 24-hour period shown in the attached
log.


Cheers,
Dick Johnson

Penguin : Linux version 2.3.13 on an i686 machine (400.59 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.
Reference time = Fri Oct 15 16:14:18 1999
My time = Fri Oct 15 16:14:19 1999
Difference = 1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Fri Oct 15 16:14:18 EDT 1999
Reference time = Sat Oct 16 12:55:16 1999
My time = Sat Oct 16 12:55:17 1999
Difference = 1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Sat Oct 16 12:55:16 EDT 1999
Reference time = Sun Oct 17 00:00:09 1999
My time = Sun Oct 17 00:00:03 1999
Difference = -6 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Mon Oct 18 00:00:14 1999
My time = Mon Oct 18 00:00:01 1999
Difference = -13 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Tue Oct 19 00:00:15 1999
My time = Tue Oct 19 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Oct 20 00:00:15 1999
My time = Wed Oct 20 00:00:00 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Thu Oct 21 00:00:14 1999
My time = Thu Oct 21 00:00:01 1999
Difference = -13 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Fri Oct 22 00:00:15 1999
My time = Fri Oct 22 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sat Oct 23 00:00:15 1999
My time = Sat Oct 23 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sun Oct 24 00:00:15 1999
My time = Sun Oct 24 00:00:00 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Mon Oct 25 00:00:14 1999
My time = Mon Oct 25 00:00:01 1999
Difference = -13 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Oct 27 00:00:29 1999
My time = Wed Oct 27 00:00:00 1999
Difference = -29 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Oct 27 16:39:38 1999
My time = Wed Oct 27 16:39:39 1999
Difference = 1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Wed Oct 27 16:39:38 EDT 1999
Reference time = Thu Oct 28 00:00:08 1999
My time = Thu Oct 28 00:00:03 1999
Difference = -5 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Fri Oct 29 00:00:16 1999
My time = Fri Oct 29 00:00:01 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sat Oct 30 00:00:15 1999
My time = Sat Oct 30 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sun Oct 31 00:00:14 1999
My time = Sun Oct 31 00:00:00 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sun Oct 31 21:54:38 1999
My time = Sun Oct 31 22:54:39 1999
Difference = 3601 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Sun Oct 31 21:54:38 EST 1999
Reference time = Mon Nov 1 00:00:10 1999
My time = Mon Nov 1 00:00:09 1999
Difference = -1 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Tue Nov 2 00:00:09 1999
My time = Tue Nov 2 00:00:04 1999
Difference = -5 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Nov 3 00:00:15 1999
My time = Wed Nov 3 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Thu Nov 4 00:00:15 1999
My time = Thu Nov 4 00:00:00 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Fri Nov 5 07:48:55 1999
My time = Fri Nov 5 07:48:56 1999
Difference = 1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Fri Nov 5 07:48:55 EST 1999
Reference time = Sat Nov 6 00:00:13 1999
My time = Sat Nov 6 00:00:03 1999
Difference = -10 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.4.101)
Reference time = Sun Nov 7 00:00:13 1999
My time = Sun Nov 7 00:00:01 1999
Difference = -12 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Mon Nov 8 00:00:15 1999
My time = Mon Nov 8 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Mon Nov 8 16:15:15 1999
My time = Mon Nov 8 16:15:14 1999
Difference = -1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Mon Nov 8 16:15:15 EST 1999
Reference time = Mon Nov 8 16:17:01 1999
My time = Mon Nov 8 16:17:01 1999
Difference = 0 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Mon Nov 8 16:17:01 EST 1999
Reference time = Tue Nov 9 00:00:08 1999
My time = Tue Nov 9 00:00:03 1999
Difference = -5 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Nov 10 00:00:35 1999
My time = Wed Nov 10 00:00:21 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Thu Nov 11 00:00:15 1999
My time = Thu Nov 11 00:00:00 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Fri Nov 12 00:00:15 1999
My time = Fri Nov 12 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Fri Nov 12 11:16:07 1999
My time = Fri Nov 12 11:16:07 1999
Difference = 0 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Fri Nov 12 11:16:07 EST 1999
Reference time = Sat Nov 13 00:00:08 1999
My time = Sat Nov 13 00:00:01 1999
Difference = -7 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Sun Nov 14 00:00:15 1999
My time = Sun Nov 14 00:00:00 1999
Difference = -15 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Mon Nov 15 00:00:14 1999
My time = Mon Nov 15 00:00:01 1999
Difference = -13 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Tue Nov 16 00:00:14 1999
My time = Tue Nov 16 00:00:01 1999
Difference = -13 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Nov 17 00:00:15 1999
My time = Wed Nov 17 00:00:01 1999
Difference = -14 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.135.130)
Reference time = Wed Nov 17 15:12:19 1999
My time = Wed Nov 17 15:12:18 1999
Difference = -1 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Wed Nov 17 15:12:19 EST 1999
Reference time = Thu Nov 18 00:00:05 1999
My time = Thu Nov 18 00:00:00 1999
Difference = -5 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.4.103)
Reference time = Thu Nov 18 08:34:39 1999
My time = Thu Nov 18 08:34:39 1999
Difference = 0 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Thu Nov 18 08:34:39 EST 1999
Reference time = Thu Nov 18 11:21:45 1999
My time = Thu Nov 18 11:21:45 1999
Difference = 0 seconds
Time set by 132.163.135.130 (132.163.135.130)
Setting hardware clock to Thu Nov 18 11:21:45 EST 1999
Reference time = Fri Nov 19 00:00:08 1999
My time = Fri Nov 19 00:00:00 1999
Difference = -8 seconds
Time set by time-A.timefreq.bldrdoc.gov (132.163.4.101)
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