_logger.fine("sub-token stream: " + tokenString.toString());
try {
// parse
ParseListener listener = new ParseListener();
DateParser parser = new DateParser(stream, listener);
DateParser.parse_return parseReturn = parser.parse();
Tree tree = (Tree) parseReturn.getTree();
_logger.fine("AST: " + tree.toStringTree());
// we only continue if a meaningful syntax tree has been built