server with a date in 2007 was producing the output
|_ http-date: Sun, 07 Jan 2007 08:17:36 GMT; -918d13h46m40s from local time.
Now it is
|_ http-date: Sun, 07 Jan 2007 09:01:44 GMT; -2y187d13h46m40s from local time.
parses an HTTP date in any of three possible formats.
http-date.nse gets the Date: header field value from and HTTP server,
then displays it with how much it differs from local time.