---
name: "clockdiff"
section: "8"
platform: "linux"
package: "iputils"
version: "20250605-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/clockdiff"
---

# clockdiff(8)

measure clock difference between hosts

## NAME

clockdiff - measure clock difference between hosts

## SYNOPSIS

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

## DESCRIPTION

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

## OPTIONS

- **-o**

  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).

- **-o1**

  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 Linux.

**-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.

- **-I**

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

- **-h**, **--help**

  Print help and exit.

- **-V**, **--version**

  Print version and exit.

## WARNINGS

• 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.

## SEE ALSO

[**ping**(8)](/ping/8.md), [**arping**(8)](/arping/8.md), [**tracepath**(8)](/tracepath/8.md).

## REFERENCES

\[1\] ICMP ECHO, RFC0792, page 14.

\[2\] ICMP TIMESTAMP, RFC0792, page 16.

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

## AUTHOR

**clockdiff** was compiled by Alexey Kuznetsov \<kuznet@ms2.inr.ac.ru\>. It was based on code borrowed from BSD **timed** daemon.

## SECURITY

**clockdiff** requires CAP\_NET\_RAW and CAP\_SYS\_NICE capabilities to be executed. It is safe to be used as set-uid root.

## AVAILABILITY

**clockdiff** is part of *iputils* package.