create table words (word varchar2(20), date_added varchar2(20))

create or replace trigger add_word   
before insert on words  
for each row     
begin     
    :new.date_added :=TO_CHAR(CURRENT_DATE,  'DD-MM-YYYY HH:MI:SS');   
end;

insert into words(word) values('test')

insert into words(word) values('hello')

select * from words