You can use the $ctime(text) identifier to compare dates.
$ctime uses standard Unix timestamps, which are the seconds elapsed since midnight, January 1, 1970 to your specified date.

The only downside is that you can only compare dates from January 1, 1970 to January 19, 2038.

alias comparedate {
  if ($ctime($1) > $ctime($2)) return 1
  elseif ($ctime($1) < $ctime($2)) return 2
  else return 3
}