DATE-FORMAT

What it does

Sends a standard GET request and checks whether the Date response header uses the preferred IMF-fixdate format.

GET / HTTP/1.1\r\n
Host: localhost:8080\r\n
\r\n

The test inspects the Date header value in the response.

What the RFC says

“An HTTP-date value represents time as an instance of Coordinated Universal Time (UTC). The first two formats [IMF-fixdate and rfc850-date] indicate UTC by the three-letter abbreviation for Greenwich Mean Time, ‘GMT’… A recipient that parses a timestamp value in an HTTP field MUST accept all three HTTP-date formats.” – RFC 9110 §5.6.7

“HTTP-date = IMF-fixdate / obs-date” – RFC 9110 §5.6.7

“A sender MUST generate timestamps in the IMF-fixdate format.” – RFC 9110 §5.6.7 (quoted from RFC 7231 §7.1.1.1, carried forward)

The preferred format is IMF-fixdate:

Sun, 06 Nov 1994 08:49:37 GMT

Why it matters

While all three date formats are valid for recipients to accept, senders (including origin servers) should generate the IMF-fixdate format. Servers using obsolete formats (RFC 850 or asctime) are technically non-conforming senders, though recipients must still parse them.

Verdicts

• Pass – Date header present and uses IMF-fixdate format
• Warn – Date header missing or uses a non-standard format

Sources

• RFC 9110 §5.6.7
• RFC 9110 §6.6.1