Strange behavior with to_char and dates

Hello,

To day we are the 9th of January 2009.
The following request preformed on a version 8.0.8 or on 8.3.5 gives the same strange result.

As you can see below,
the request "to_char((current_date - 11), 'DD MM IYYY')" gives "29 12 2009" instead of "29 12 2008". With 12 or with 8
theresult is 
good.

EXTRACT is a good workaround.
What did I wrong?
Is my request bad or is it a bug?

Best regards,

select
to_char(current_date, 'DD MM IYYY') as good_curdate,
current_date - 10 as good_cur_10,
to_char((current_date - 10), 'DD MM IYYY') as bad_date1_10,
to_char((date(now())-10), 'DD MM IYYY') as bad_date2_10,
to_char((current_date - 13), 'DD MM IYYY') as good_date_13,
to_char((current_date - 12), 'DD MM IYYY') as good_date_12,
to_char((current_date - 11), 'DD MM IYYY') as bad_date_11,
to_char((current_date - 10), 'DD MM IYYY') as bad_date_10,
to_char((current_date - 9), 'DD MM IYYY') as bad_date_9,
to_char((current_date - 8), 'DD MM IYYY') as good_date_8,
to_char((current_date - 7), 'DD MM IYYY') as good_date_7,
EXTRACT(day FROM (date(now())-10)  ) as good_day_10,
EXTRACT(month FROM (date(now())-10)  ) as good_month_10,
EXTRACT(YEAR FROM (date(now())-10)  ) as good_year_10;

good_curdate      : "09 01 2009"
good_cur_10        : "2008-12-30"
bad_date1_10    : "30 12 2009"
bad_date2_10    : "30 12 2009"
good_date_13    : "27 12 2008"
good_date_12    : "28 12 2008"
bad_date_11        : "29 12 2009"
bad_date_10        : "30 12 2009"
bad_date_9        : "31 12 2009"
good_date_8        : "01 01 2009"
good_date_7        : "02 01 2009"
good_day_10        : 30
good_month_10    : 12
good_year_10    : 2008

Denis Percevault
d.percevault@pnsconcept.fr