To update the time on a Linux installation, simply run the following command:
$ sudo ntpdate <time server address>
Replacing <time server address> with a valid NTP time server address.
eg:
$ sudo ntpdate pool.ntp.org
If you only want to query the time, without updating your system, use the following command:
$ ntpdate -q pool.ntp.org
To update the time, without outputting any log information to standard output (handy for a cron job), use the following command:
$ sudo ntpdate -s pool.ntp.org