According to the latest WebDAV specification (RFC4918),
timestamp string in the getlastmodified property is formatted
as rfc1123-date, such as "Sun, 06 Nov 1994 08:49:37 GMT".
However, to process responses from servers in the older style
format specified in RFC2518, timestamps in the HTTP-date format
had better be accepted.

As described in the libcurl api documentation, curl_getdate() can handle
timestamp strings in HTTP-date formats, including rfc1123-date.

https://www.rfc-editor.org/rfc/rfc4918#section-15.7
https://www.rfc-editor.org/rfc/rfc2518.html#section-13.7
https://curl.se/libcurl/c/curl_getdate.html