A PERIOD(TIME(n) [WITH TIME ZONE]) or PERIOD(TIMESTAMP(n) [WITH TIME ZONE]) value can be cast as TIME[(n)] [WITH TIME ZONE] using the CAST function. The source last value must be equal to the source beginning bound; otherwise, an error is reported.
If the target precision is higher than the source precision, trailing zeros are added in the result to adjust the precision. If the target precision is lower than the source precision, an error is reported.
If the source type is PERIOD(TIME(n) [WITH TIME ZONE]) or PERIOD(TIMESTAMP(n) [WITH TIME ZONE]), the result time portion is obtained from time portion of the source beginning bound. If both the source and target type are WITH TIME ZONE, the result time zone field is set to the time zone displacement of the source beginning bound. If only the target type is WITH TIME ZONE, the result time zone field is set to the current session time zone displacement.
If the source type is PERIOD(DATE), an error is reported.