get the remote time of the retrieved document
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_FILETIME, long *timep);
Pass a pointer to a long to receive the remote time of the retrieved document
(in number of seconds since 1 jan 1970 in the GMT/UTC time zone). If you get
-1, it can be because of many reasons (it might be unknown, the server might
hide it or the server doesn't support the command that tells document time
etc) and the time of the document is unknown.
Note that you must tell the server to collect this information before the
transfer is made, by using the CURLOPT_FILETIME(3) option to
curl_easy_setopt(3) or you will unconditionally get a -1 back.
Added in 7.5
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.