explicit casts

Hi there,

I installed postgresql 8.4 on my box and now i have troubles with the
following query regarding explicit casts.

select to_char(trunc(to_date(:the_date, 'yyyy-mm-dd'), 'Month'),
'fmMonth') as month,
to_char(trunc(to_date(:the_date, 'yyyy-mm-dd'), 'Month'), 'YYYY')
as year,
to_char(trunc(to_date(:the_date, 'yyyy-mm-dd'), 'Month'), 'J') as
first_julian_date_of_month,
to_char(last_day(to_date(:the_date, 'yyyy-mm-dd')), 'DD') as
num_days_in_month,
to_char(trunc(to_date(:the_date, 'yyyy-mm-dd'), 'Month'), 'D') as
first_day_of_month,
to_char(last_day(to_date(:the_date, 'yyyy-mm-dd')), 'DD') as last_day,
trunc(add_months(to_date(:the_date, 'yyyy-mm-dd'), 1),'Day') as
next_month,
trunc(add_months(to_date(:the_date, 'yyyy-mm-dd'), -1),'Day') as
prev_month,
trunc(to_date(:the_date, 'yyyy-mm-dd'), 'year') as beginning_of_year,
to_char(last_day(add_months(to_date(:the_date, 'yyyy-mm-dd'), -1)),
'DD') as days_in_last_month,
to_char(add_months(to_date(:the_date, 'yyyy-mm-dd'), 1), 'fmMonth')
as next_month_name,
to_char(add_months(to_date(:the_date, 'yyyy-mm-dd'), -1),
'fmMonth') as prev_month_name
from dual

the value assigned to the variable :the_date is '2010-01-05'

The error is

Error: Ns_PgExec: result status: 7 message: ERROR: function
to_date(timestamp with time zone, unknown) does not exist
LINE 1: select to_date(date_trunc('month',add_months( $1 ,1)),'YYYY-...
^
HINT: No function matches the given name and argument types. You might
need to add explicit type casts.
QUERY: select to_date(date_trunc('month',add_months( $1
,1)),'YYYY-MM-DD') - 1
CONTEXT: PL/pgSQL function "last_day" line 6 at SQL statement

how would i apply the following solution

date_trunc('month', p_date_in + interval '1 month')::date - 1

to fix the query above?

cheers,
iuri