timestamp in trigger

In a ON UPDATE trigger on Toto table , i insert in a log a timestamp
like this

CREATE TABLE LogProtocole (
logprotocole_id SERIAL,
logprotocole_message text,
logprotocole_date timestamp,
CONSTRAINT pk_logprotocole PRIMARY KEY (logprotocole_id)

);

insert into logprotocole (
logprotocole_message,logprotocole_date) select 'toto','now';

when i use it x time , the logprotocole_date take value from an old one.

( there is lot of triggers on Toto table : on insert,on delete,before
update ,after update )