CLOCKDIFF(8)                         iputils                        CLOCKDIFF(8)

       clockdiff - measure clock difference between hosts

       clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}

       clockdiff Measures clock difference between us and destination with 1
       msec resolution using ICMP TIMESTAMP [2] packets or, optionally, IP
       TIMESTAMP option [3] option added to ICMP ECHO. [1]

           Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP messages.
           It is useful with some destinations, which do not support ICMP
           TIMESTAMP (f.e. Solaris <2.4).

           Slightly different form of -o, namely it uses three-term IP TIMESTAMP
           with prespecified hop addresses instead of four term one. What flavor
           works better depends on target host. Particularly, -o is better for

       -T, --time-format ctime iso
           Print time stamp in output either ISO-8601 format or classical ctime
           format. The ctime format is default. The ISO time stamp includes
           timezone, and is easier to parse.

           Alias of --time-format iso option and argument.

       -h, --help
           Print help and exit.

       -V, --version
           Print version and exit.

           • Some nodes (Cisco) use non-standard timestamps, which is allowed by
           RFC, but makes timestamps mostly useless.

           • Some nodes generate messed timestamps (Solaris>2.4), when run
           xntpd. Seems, its IP stack uses a corrupted clock source, which is
           synchronized to time-of-day clock periodically and jumps randomly
           making timestamps mostly useless. Good news is that you can use NTP
           in this case, which is even better.

           • clockdiff shows difference in time modulo 24 days.

       ping(8), arping(8), tracepath(8).

       [1] ICMP ECHO, RFC0792, page 14.

       [2] ICMP TIMESTAMP, RFC0792, page 16.

       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.

       clockdiff was compiled by Alexey Kuznetsov <>. It was
       based on code borrowed from BSD timed daemon.

       clockdiff requires CAP_NET_RAW capability to be executed. It is safe to
       be used as set-uid root.

       clockdiff is part of iputils package.

iputils s20200821                                                   CLOCKDIFF(8)