public function parse(\Doctrine\ORM\Query\Parser $parser)
{
$parser->match(Lexer::T_IDENTIFIER);
$parser->match(Lexer::T_OPEN_PARENTHESIS);
$this->datetime = $parser->ArithmeticExpression();
$parser->match(Lexer::T_COMMA);
$this->fmt = $parser->StringExpression();
$parser->match(Lexer::T_CLOSE_PARENTHESIS);
}