clockspeed uses a hardware tick counter to compensate for a persistently fast
or slow system clock. Given a few time measurements from a reliable source,
it computes and then eliminates the clock skew.

sntpclock checks another system's NTP clock, and prints the results in a
format suitable for input to clockspeed. sntpclock is the simplest
available NTP/SNTP client.

taiclock and taiclockd form an even simpler alternative to SNTP. They are
suitable for precise time synchronization over a local area network, without
the hassles and potential security problems of an NTP server.