date and timestamps are always tricky, especially if there are timezones.
Do you checked that you read the same data?
It could be a driver issue, or the session is different openend (i.e. different datasource definition or just different default of the datasource subsystem).
Do you read the timestamp as String? What if you read it as timestamp do you get exact the same?
It could also be worth trying with parameters as -Duser.timezone=EET (or appropriate) as some components might have become more picky in later versions.
You might also want to check the DB on a session level from some v$-view if there is some specific NLS setting in the connection that differ between AS5 and AS7