[oracle] How can I set a custom date time format in Oracle SQL Developer?

With Oracle SQL Developer 3.2.20.09, i managed to set the custom format for the type DATE this way :

In : Tools > Preferences > Database > NLS

Or : Outils > Préférences > Base de donées > NLS

YYYY-MM-DD HH24:MI:SS

Settings Menu screenshot

Note that the following format does not worked for me :

DD-MON-RR HH24:MI:SS

As a result, it keeps the default format, without any error.