SQL : Get Last Update TimeStampe For A Table

I have some Oracle tables that have no datestamp on them
that would display the last update of that row. 
Here is a query for that:
SELECT SCN_TO_TIMESTAMP( ORA_ROWSCN )
FROM YOURTABLE;
Sample output would look something like:
4/16/2014 9:01:26.000000000 AM
Of course, you can add a where clause to determine update
for your particulars.
For more information: SCN_TO_TIMESTAMP