TO_CHAR or TO_DATE

Hi,

Is the any similar function to 'to_char' and to_date' from Oracle in
Postgresql?

I have a problem insert only month-year.

create table blah
(id varchar(10),month date,week int4,amount float8
);

insert into blah
(id, month, week, amount)
values
('1','MAR-1999',1,,3000);

I got error message : Bad date external representation MAR-1999

How to do it the right way to insert only month and year?

Regards,
Chai