A PERIOD(DATE) or PERIOD(TIMESTAMP(n) [WITH TIME ZONE]) value can be cast as DATE using the CAST function. The source last value must be equal to the source beginning bound; otherwise, an error is reported.
If the source type is PERIOD(DATE), the result is the source beginning bound.
If the source type is PERIOD(TIMESTAMP(n) [WITH TIME ZONE]), the result is the date portion of the source beginning bound after adjusting to the current session time zone.
If the source type is PERIOD(TIME(n) [WITH TIME ZONE]), an error is reported.