PostgreSQL : cast string to date DD/MM/YYYY

https://www.postgresql.org/docs/8.4/functions-formatting.html

SELECT to_char(date_field, 'DD/MM/YYYY')
FROM table

A DATE column does not have a format. You cannot specify a format for it.

You can use DateStyle to control how PostgreSQL emits dates, but it's global and a bit limited.

Instead, you should use to_char to format the date when you query it, or format it in the client application. Like:

SELECT to_char("date", 'DD/MM/YYYY') FROM mytable;

e.g.

regress=> SELECT to_char(DATE '2014-04-01', 'DD/MM/YYYY');
  to_char   
------------
 01/04/2014
(1 row)

The documentation says

The output format of the date/time types can be set to one of the four styles ISO 8601, SQL (Ingres), traditional POSTGRES (Unix date format), or German. The default is the ISO format.

So this particular format can be controlled with postgres date time output, eg:

t=# select now();
              now
-------------------------------
 2017-11-29 09:15:25.348342+00
(1 row)

t=# set datestyle to DMY, SQL;
SET
t=# select now();
              now
-------------------------------
 29/11/2017 09:15:31.28477 UTC
(1 row)

t=# select now()::date;
    now
------------
 29/11/2017
(1 row)

Mind that as @Craig mentioned in his answer, changing datestyle will also (and in first turn) change the way postgres parses date.