Off by one error in parsing of 'Date(a,b,c,d,e,f)' format.

Some weird json producers produce *strings* of that format instead of just
date strings ('yyyy-mm-dd hh:mm:ss') or javascript objects (new
Date(a,b,c,d,e,f)).  These obviously didn't happen very much or I would have
noticed that when we parsed them, we're off by a month :)