Yes, you need the DD-MON-RR format in the database now - It was a year 2k requirement so that any year typed in with a 2 digit year would be interpreted as:

> 50 = 19xx
< 50 = 20xx

I believe it needs to be set in the client environment too.

Oracle stores dates as seconds since 4719bc (Roughly?) so NLS_DATE_FORMAT is purely a date mask.