One of the most super annoying things about Oracle SQL developer is that it defaults to a not so useful (at least to me) date format along the lines of 15-NOV-11. I prefer to see something helpful like an ISO 8601 formatted date/time.
The solution is to, in Oracle SQL Developer, go to: Tools > Preferences.
Then in the Preferences dialog, select Database and drill down to NLS.
In the NLS parameters you'll be able to set the Date Format to:
I have found that on some systems, you may need to use a setting like: