Is there a better way to do this?

Hi all

I want to implement something like the following:

CREATE OR REPLACE FUNCTION AddDays
        (TIMESTAMP WITHOUT TIME ZONE
        , INT)
RETURNS TIMESTAMP WITHOUT TIME ZONE AS '
DECLARE
        time ALIAS FOR $1;
        days ALIAS FOR $2;
BEGIN
        RETURN time+days*24*3600*''1 second''::INTERVAL;
END;
' LANGUAGE 'plpgsql';

Basically the function takes two parameters, and add the second one (as
days) onto the first one (as timestamp without  timezone)
I don't really like this implementation. Is there a more concise way to
do this?

Thanks

Wei