NAME
  rdate - set the system's date from a remote host

SYNOPSIS
  rdate [-46acnpsuv] [-b sec] [-o port] [-t msec] host

DESCRIPTION
  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 868 TCP protocol server, which is usually implemented as a built-in
  service of inetd(8), or an RFC 5905 protocol SNTP/NTP server. By default, rdate uses the RFC 868 TCP
  protocol.

  OpenRdate supports IPv4 and IPv6 protocols.

OPTIONS
  -4  Force rdate to use IPv4 addresses only.
  -6  Force 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.
  -b sec  Use adjtime if clock difference is at most sec seconds or hop if difference is greater. This
          is the same as including of removing the option -a, based on clock difference.
  -c  Correct leap seconds. Sometimes required when synchronizing to an NTP server. When synchronizing
      using the RFC 868 protocol, use this option only if the server does not correctly account for leap
      seconds. You can determine if you need this parameter if you sync against an NTP server (with this
      parameter) or (recommended) check with a local radio controlled watch or phone service.
  -n  Use SNTP (old RFC 2030, currently RFC 5905) instead of the RFC 868 time protocol.
  -o port  Use port 'port' instead of port 37.
  -p  Do not set, just print the remote time.
  -s  Do not print the time.
  -u  Use UDP instead of TCP as transport.
  -t msec  Does not set time if it took more than msec milliseconds to fetch time from network.
  -v  Verbose output. Always show the adjustment.

FILES
  /var/log/wtmp  Record of date resets and time changes.

EXAMPLES
  To get the legal time in Germany, set the /etc/localtime symlink
  to /usr/share/zoneinfo/right/Europe/Berlin and issue the following command:

    # rdate -ncv 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.

  To gradually adjust time once an hour after the first "step" adjustment, put the following line
  into root's crontab:

    58  *  *  *  *  rdate -ncav ptbtime1.ptb.de | logger -t NTP

  To set the time through an ssh tunnel, use something like so:

    ssh -f -L 10037:time.example.com:37 tyr.example.com sleep 10
    rdate -a -o 10037 localhost

SEE ALSO
  date(1), adjtime(2), inetd(8), ntpd(8), ntpdate(8), timed(8)

AUTHORS
  OpenRdate was originally developed by David Snyder and was based in rdate, created by Christos Zoulas
  in 1994 for OpenBSD Project. Over time, OpenRdate got several contributions from people.

  This manual page was written by Christos Zoulas. It was changed by Anibal Monsalve Salazar for
  the Debian Project and updated by Joao Eriberto Mota Filho.
