Accurate time without a network connection?

[Kent Stewart]

On Tuesday 22 April 2003 12:44 pm, David Kelly wrote:
> On Tue, Apr 22, 2003 at 03:26:19PM -0400, Charles Swiger wrote:
> > Ok.  If you run NTPD with only the local hardware clock for a
> > reference, wait for a week, and then see how the intrinsic drift of
> > the hardware compares with "real time" (using your watch or some
> > other time source), you can adjust /etc/ntp.drift by hand.  This
> > isn't going to be perfect, but it's going to be much more accurate
> > than doing nothing.
>
> Good. But already tried that. The situation is multiple systems have
> to run with something near the same time, but no bidirectional
> contact. And need to operate for years. Letting ntpd tune itself and
> then free run works much better than the system clock alone but only
> good for weeks, not months.
>
> As for exactly what time the systems have, it doesn't much matter as
> long as they all have the same time.

It sounds like you really need an external clock that is very stable. 
There was a discussion on -hackers a long time ago about doing 
something like that. I think they were using a gps based clock for a 
reference.

If you don't have access to a common time, nothing short of access to 
WWVB (the Navy Time Radio Station) would keep your time current.

Kent

-- 
Kent Stewart
Richland, WA

http://users.owt.com/kstewart/index.html