rdate — set the
    system's date from a remote host
rdate displays and sets the local date and
    time from the host name or address given as the argument. The time source
    may be an RFC 5905 protocol SNTP/NTP server or an RFC 868 TCP protocol
    server, which is usually implemented as a built-in service of
    inetd(8).
    By default, rdate uses the RFC 5905 SNTP/NTP
    protocol.
The options are as follows:
  -4 
  - Forces 
rdate to use IPv4 addresses only. 
  -6 
  - Forces 
rdate to use IPv6 addresses only. 
  -a 
  - Use the
      adjtime(2)
      call to gradually skew the local time to the remote time rather than just
      hopping.
 
  -c 
  - Correct leap seconds. This should be used only when synchronizing to a
      server which does not correctly account for leap seconds.
 
  -n 
  - Use SNTP (RFC 5905) instead of the RFC 868 time protocol. This is the
      default. This protocol counts 32 bits of seconds from January 1, 1900 and
      will rollover in March 2036.
 
  -o 
  - Use an RFC 868 TCP protocol server instead of SNTP. This protocol is
      obsolete as it is not capable of representing dates past January 19, 2038
      03:14:07 GMT.
 
  -p 
  - Do not set, just print the remote time.
 
  -s 
  - Do not print the time.
 
  -v 
  - Verbose output. Always show the adjustment.
 
  - /var/log/wtmp
 
  - record of date resets and time changes
 
To get the legal time in Germany, set the
    /etc/localtime symlink to
    /usr/share/zoneinfo/Europe/Berlin and issue the
    following command:
# rdate -v
  ptbtime1.ptb.de
The command of course assumes you
    have a working internet connection and DNS set up to connect to the server
    at
    Physikalisch-Technische
    Bundesanstalt in Braunschweig, Germany.