datestyle on windows environment: how to set?

Hello,

I want to set the datestyle = 'ISO, European' for all my databases. I
put that configuration into postgresql.conf file, but I didn't succeed.
After rebooting all dates are like that:

YYYY-MM-DD

I'd like to have

DD-MM-YYYY for my timestamp field.

I have the latest version of pgsql and perl.

Hereafter is an extract of my postgresql.conf file.

Thanks and best regards,
Filippo

# - Locale and Formatting -

datestyle = 'ISO, European'
#timezone = unknown            # actually, defaults to TZ                # environment setting
#australian_timezones = off
#extra_float_digits = 0            # min -15, max 2
#client_encoding = sql_ascii        # actually, defaults to database                # encoding

# These settings are initialized by initdb -- they might be changed
lc_messages = 'C'            # locale for system error message                # strings
lc_monetary = 'C'            # locale for monetary formatting
lc_numeric = 'C'            # locale for number formatting
lc_time = 'C'                # locale for time formatting