easy:SetOpt_FileTime -- get the modification time of the remote resource
Pass a value. If it is 1, libcurl will attempt to get the modification time of
the remote document in this operation. This requires that the remote server
sends the time or replies to a time querying command. The
easy:GetInfo() function with the #CURLINFO_FILETIME
argument can be used after a transfer to extract the received time (if any).