8.6.4 Set time (NTP)
Accurate Date and Time HOWTO.
220.127.116.11 Set time with permanent Internet connection
Set system clock to the correct time automatically via a remote server:
# ntpdate server
This is good to have in
/etc/cron.daily/ if your system has a
permanent Internet connection.
18.104.22.168 Set time with sporadic Internet connection