This is from the link

1/8/1999	January 8 in `MDY` mode; August 1 in `DMY` mode
1/18/1999	January 18 in `MDY` mode; rejected in other modes
01/02/03	January 2, 2003 in `MDY` mode; February 1, 2003 in `DMY` mode; February 3, 2001 in `YMD` mode

you can run this

select '01/01/2009'::date, '01-01-2009'::date

You can change the output for the client..

http://www.postgresql.org/docs/current/static/runtime-config-client.html#GUC-DATESTYLE

Bernard Barton wrote:.

I'm currently porting an Informix based application to PostgreSQL 8.3. 
All of the dates processed by the application are in the mmddyyyy
format.  According to the date input table at the link below, the
mmddyyyy format is not listed.  The yyyymmdd format is supported, but
I'd have to modify a LOT of code to change the format, which I'm trying
to avoid.  Is there any way to get PG to work with the mmddyyyy date
format?  I know I can use the to_date function, but again, it would be
MUCH simpler if PG worked with this format.

-Thanks

http://www.postgresql.org/docs/current/static/datatype-datetime.html#DATATYPE-DATETIME-DATE-TABLE