====== set time ======
<code>
date --set="23 June 1988 10:00:00"
date --set="10:00:00"

Set the Hardware Clock to the current System Time
# hwclock --systohc

Set the System Time from the Hardware Clock.
# hwclock --hctosys
</code>

====== update via ntp ======
via ntpd
<code>
sudo service ntp stop
sudo ntpd -gq
sudo service ntp start
</code>

via ntpdate
<code>
ntpdate ntp.ubuntu.com
</code>
====== ntp server ======
如果出現 ''Server dropped: strata too high''，在 ntp.conf 新增以下
<code>
server 127.127.1.0
fudge 127.127.1.0 stratum 8
</code>


參考
  * http://superuser.com/questions/302396/how-to-set-current-time-on-linux
  * http://askubuntu.com/questions/254826/how-to-force-a-clock-update-using-ntp
  * http://superuser.com/questions/181341/how-to-check-if-ntp-adjusted-system-time-on-linux