Yes as I understand that date time in listing has no relation to last modified time:

void Main()
{
   Uri uri = new Uri("ftp://ftp.prolib.de/Public/Why_VFP");
   FtpWebRequest req = (FtpWebRequest)FtpWebRequest.Create(uri); 
	 
   req.Credentials = new NetworkCredential ("anonymous", "password");
   req.Method = WebRequestMethods.Ftp.GetDateTimestamp;
   
   using(FtpWebResponse resp  = (FtpWebResponse)req.GetResponse())
	 {
	  DateTime result = resp.LastModified;
		Console.WriteLine (result);
	 }
}

I will provide a more detailed code later (after dinner and match on TV:)
Cetin