[Tfug] A sense of time

[Louis Taber]

Time again,

I couldn't locate the documentation, but I seem to remember that you can
slew the clock to set it to a new time on some UNIX type systems.  So the
time at any given instant is moving toward the new setting and not making a
finite jump.  With ntp (Network Time Protocol) it is not really an issue.
ntp in general is a MUCH better way to go than trying to set the time
yourself.

If you really want to know what time it is get a GPS receiver, not an
"Atomic Clock".  An "Atomic Clock" looks at a single 60kHz signal from Fort
Collins CO.  This signal is usually not adjusted for the signals time of
flight.  A GPS receiver figures out where it is specifically  by looking at
the various time of flights.  If you have access to L2 it also compensates
for the lensing effects of the atmosphere.  Internally a GPS receiver will
know what time it is to about 10-20ns.  About the time it takes light to
cross a medium size room.  A system with a GPS receiver connected to it with
a PPS (pulse per second) and serial connection can be set up as a stratum 1
ntp server.  If this is on a fast local area network, all of the connected
systems can be quite accurate as well.  At least good enough to snipe on
e-bay.  - Louis