I have this anonymous block:
DECLARE V_DATA DATE; BEGIN V_DATA := \'01-GEN-2000\'; HR.STATISTICHE.RATINGOPERATORI (V_DATA); COMMIT; END;
To generate random date you can use
select to_date('2010-01-01', 'yyyy-mm-dd')+trunc(dbms_random.value(1,1000)) from dual
or for random datetime
select to_date('2010-01-01', 'yyyy-mm-dd')+dbms_random.value(1,1000) from dual