taiclockd 1 user commands djbwares
taiclockd announce the system's clock through TAICLOCK
`taiclockd`

## Description

`taiclockd` announces the local UNIX clock through the TAICLOCK protocol. It accepts TAICLOCK requests from hosts around the Internet, and responds with the system's current time.

Normally `taiclockd` is run via a server program such as `udp-socket-listen` to listen for TAICLOCK queries from hosts around the Internet. It understands the `LISTEN_PID` and `LISTEN_FDS` environment variable convention for having an already-listening socket passed to it by such a program, and uses the last open file descriptor in the list that refers to a UDP/IPv6 socket. If no such open file descriptor is provided it falls back to opening its own UDP/IPv6 socket, bound to port 4014 of the IP address given by the value of the `IP` environment variable.

`taiclockd` is capable of handling both IPv4 and IPv6 requests on combined-stack systems.

Do not run `taiclockd` if your system is tuned by `xntpd`. See Daniel J. Bernstein's UTC, TAI, and UNIX time paper for further discussion.

## Security

`taiclockd` does not need to run as root.

## History

`taiclockd` was originally part of Daniel J. Bernstein's clockspeed toolset in 1998. It was converted to IPv6 in 2025 with the original IPv4-only tool renamed to taiclock4d 1.

## Author

Original code and documentation by Daniel J. Bernstein. Documentation modernizations by Jonathan de Boyne Pollard.