From LQWiki

The ntpdate tool can be used to obtain the time from an Internet Time Server:

ntpdate -b ntp.blueyonder.co.uk

Using the cron

To configure the system to synchronize the clock with an Internet Time Server, every morning add the following entry to the /etc/crontab configuration file:

1. m h dom mon dow user command

57 3 * * * root /usr/sbin/ntpdate ntp.blueyonder.co.uk

Public Internet Time Servers

uk.pool.ntp.org (This points to a random UK based time server)