Assume p is a PERIOD(DATE) column in table t1 with a value of PERIOD '(2005-02-02, 2006-02-03)' and the current session time zone displacement is INTERVAL -'08:00' HOUR TO MINUTE.
In the following example, a PERIOD(DATE) column is cast as PERIOD(TIMESTAMP(6)). The date portion is obtained from the source for the corresponding result element and the time portions are set to zero.
SELECT CAST(p AS PERIOD(TIMESTAMP(6))) FROM t1;
The following is returned:
('2005-02-02 00:00:00.000000', '2006-02-03 00:00:00.000000')