# WHATPORT(13)

## NAME

port 13 — Daytime — Daytime — connect and the server prints the current date and time as human-readable text, then hangs up.

Protocol: TCP/UDP  
IANA registry

## DESCRIPTION

RFC 867 specifies Daytime as an ASCII time-of-day string returned on connect, with no request format and no defined layout for the string itself. NIST still runs it on time.nist.gov as part of the Internet Time Service, in a fixed format that includes a Modified Julian Date and a UTC timestamp. It was an inetd built-in on classic UNIX and is off by default on modern systems. Because the string is unstructured and unauthenticated, it is a curiosity rather than a way to set a clock — NTP is.

## EXPOSURE

**Expose with care.** It leaks nothing worse than the host clock, but the UDP form is a spoofable reflector and the service has no modern purpose outside a deliberate public time service.

## CHECK

```sh
nc -v time.nist.gov 13
```

## SEE ALSO

- spec — [RFC 867 — Daytime Protocol](https://www.rfc-editor.org/rfc/rfc867.html) (rfc-editor.org)
- docs — [NIST Internet Time Service (ITS)](https://www.nist.gov/pml/time-and-frequency-division/time-distribution/internet-time-service-its) (nist.gov)
- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/13/> · JSON: <https://whatport.net/13.json> · full dataset: <https://whatport.net/ports.json>