autotimestamping

want an auto timestamping on my table.. SQL of create:
create table healthnotes ( "posted" timestamptz not null default
current_timestamp,
"notes" text,
primary key (posted))

was succ. but how do I set it to autotimestamp when adding entries?

tried:

insert into healthnotes values ('my text notes entry my text notes
entry my text notes entry')

but said the value for timestamp was too long
clearly the autotimestamp isn't set up yet

Michael