TOAD 7.5 and up can show TIMESTAMP and INTERVAL data in its data grids if you are using a 9.0.1 or higher Oracle client. TOAD 9.0.1 supports TIMESTAMP and INTERVAL data in its "run as script" function. TOAD versions 7.4 and previous do not support TIMESTAMP and INTERVAL data due to a limitation in their data layer.

To see timestamp/intervals in the "datatype" drop down in the Create/Alter Table window, and in the "Add Column" window, go to options → datatypes, and make sure "Include Timestamp/Interval Types" is checked.