Upgrade 7.2.1 to 7.3.4 datetime Error

Hey folks..
I have problem when upgrade from 7.2.1 to 7.3.4
with function I create...

How I can fix it ?

Thank you for any suggestion
EKo Pranoto


--------------Message Recieve----------------------
ERROR:  Function datetime(timestamp with time zone) does not exist
        Unable to identify a function that satisfies the given argument types
        You may need to add explicit typecasts

-----------------FUNCTION------start-------------
CREATE FUNCTION "set_waktu" ()
RETURNS timestamp without time zone AS 'set datestyle to ''european'';
set datestyle to ''sql'';
select datetime(now()) as result' LANGUAGE 'sql';
---------------FUNCTION--------end-------------