timep = easy:GetInfo_FileTime()
You must tell libcurl to collect this information before the transfer is made,
by using the
#CURLOPT_FILETIME option to easy:SetOpt() or
you will unconditionally get a -1 back.
#CURLINFO_FILETIME_T to be able to extract dates beyond
the year 2038 on systems using 32 bit longs.