How to quote date value?

What is correct character to quote date values in SELECT. Is is single
quote?

When I do:

SELECT '1/11/2003' AS "InvoiceDate";

the returned value is of unknown type (not a date).

Then I tried:

SELECT 1/11/2003 AS "InvoiceDate";

and the InvoiceDate was set to zero (I guess the engine divided the numbers
in date).

Then I tried:

SELECT 1-11-2003 AS "InvoiceDate";

and the numbers in date value got substracted.

Using PostgreSQL 7.4 and PgAdmin 3.

Any insight is welcome.