curl::option CurlHandle,"FILETIME"
Pass a long. If it is a non-zero value, libcurl will attempt to get the modification date of the remote document in this operation. This requires that the remote server sends the time or replies to a time querying command. The curl_easy_getinfo() function with the CURLINFO_FILETIME argument can be used after a transfer to extract the received time (if any). (Added in 7.5)