The Network Time Protocol (NTP) daemon provided by the ntp-simple package is by far the easiest way to manage the accuracy of your clock, particularly if you are connected to the internet (even if only intermittently).
The ntp-simple daemon (ntpd) effectively sets the cock by speeding it up or slowing it down depending on its natural drift so that it gets in sync and stays there. This avoids a ``sudden shock'' to the system with a dramatic change to the time, although mostly the system can handle it.
The primary configuration required is to identify an NTP server. Look at the lists at http://www.eecis.udel.edu/~ntp/, for example.
After running ntpd for a little while your clock will be set to an accurate time and will maintain an accurate time. However, if the amount of difference is too great then ntpd will not modify the clock. After setting up ntp-simple you can install ntpdate and on install (and reboot) the clock will be updated to the correct time according to the server you have chosen for ntp-simple.
With ntp-simple installed on one of your hosts, Velox (4.10.26) for example, on the local network you can now use Velox (4.10.26) as a ntp server simply by installing ntp on each machine and pointing them to Velox (4.10.26) as the server.