It may not be, in general.  In my case, I had an adjustment large
   enough that I didn't want to wait for the slow one-or-two-percent slew
   tickadj tends to use; I cranked tickadj up until the machine's
   time-of-day was ticking off seconds nearly twice as fast as my watch.

There's a good reason for `ntpdate' being in the xntp distribution.
In general, you should run it before you start xntpd.

   One thing on my
   it-would-be-nice-to-do-someday list is to look at extending things so
   that the clock tick size is kept in units much smaller than
   microseconds (perhaps 2^-32 usec) so that it can be adjusted to very
   fine precision, to match observed effective clock tick rates quite
   accurately.

There's a piece of code in recent xntpd distributions that's supposed
to simulate a phase locked loop.  Supposedly after the PLL settles it
keeps very precise time.  I haven't tried it.