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.
              SNTP will always use UDP protocol and its default port is 123.

       -o port
              Use port 'port' instead of port 37 (RFC 868) or 123 (SNTP, RFC 5905).

       -p     Do not set, just print the remote time.

       -s     Do not print the time.

       -u     Use UDP instead of TCP as transport (for RFC 868 only; see -n option).

       -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.