On Mon, 26 Jun 2006 08:08:03 -0400, "Steven M. Bellovin"
<smb@cs.columbia.edu> wrote:

> On Mon, 26 Jun 2006 14:23:53 +1000, George Michaelson <ggm@apnic.net>
> wrote:
> 
> >  
> > > I think that that's Dan's point -- /var/db/ntp.drift is for state
> > > between boots.  It's supposed to measure the difference over time
> > > between your machine's clock and reality, and you rarely switch
> > > clocks.  It isn't supposed to compensate for the errors in your ntp
> > > peers; ntp assumes that there's One True Time, and doesn't use
> > > averaging, for example.
> > > 
> > > 
> > > 		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb
> > 
> > right. so if you switch internal clock models, the ntp.drift is
> > inherently invalid, and the right thing (tm) is to junk it.
> > 
> Yes; that's what I did last night.  This morning's offsets look much
> better, though I'll see what happens during the day.
> 
After several days, it's keeping time very well, probably better than it
was before.

Again -- after switching timer type, remove your /var/db/ntp.drift file.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb