[sql] Updating a date in Oracle SQL table

I am trying to update a date in a SQL table. I am using Peoplesoft Oracle. When I run this query:

Select ASOFDATE from PASOFDATE;

I get 4/16/2012

I tried running this query

UPDATE PASOFDATE SET ASOFDATE = '11/21/2012';

but it is not working.

Does anyone know how I would change the date to the one desired?

Just to add to Alex Poole's answer, here is how you do the date and time:

    TO_DATE('31/DEC/2017 12:59:59', 'dd/mm/yyyy hh24:mi:ss')

If this SQL is being used in any peoplesoft specific code (Application Engine, SQLEXEC, SQLfetch, etc..) you could use %Datein metaSQL. Peopletools automatically converts the date to a format which would be accepted by the database platform the application is running on.

In case this SQL is being used to perform a backend update from a query analyzer (like SQLDeveloper, SQLTools), the date format that is being used is wrong. Oracle expects the date format to be DD-MMM-YYYY, where MMM could be JAN, FEB, MAR, etc..

Here is how you set the date and time:

update user set expiry_date=TO_DATE('31/DEC/2017 12:59:59', 'dd/mm/yyyy hh24:mi:ss') where id=123;