The ntpdate command sets the current system time by contacting a timeserver machine on the network. You must be root to set the system time.

# /usr/sbin/ntpdate timeserver.someplace.edu
 7 Sep 21:01:25 ntpdate[2399]: step time server 178.99.1.8
   offset 0.51 sec

To keep your system date in sync with a timeserver over long periods, use the daemon ntpd instead; see http://www.ntp.org. If you don’t know a local timeserver, search Google for “public ntp time server”.