A PERIOD(TIME(n) [WITH TIME ZONE]) value can be cast as PERIOD(TIME[(n)] [WITH TIME ZONE]) using the CAST function.
The UTC value of the source is copied to the UTC value in the result. If the target type specifies WITH TIME ZONE and the source contains time zones, the time zone displacements from the source are copied to the corresponding result elements. If the source does not contain time zones, the current session time zone displacement is copied to both result elements. For example, assume the current session time zone displacement is INTERVAL - "08:00" HOUR TO MINUTE and the source PERIOD(TIME(0) WITH TIME ZONE) has the value PERIOD '(12:12:12+08:00, 12:12:13+08:00)'. The UTC value of this source is ('04:12:12', '04:12:13'). The UTC value of the result is set to this value. On output of this result, the UTC value is adjusted to the current session time zone and the result is ('20:12:12', '20:12:13').
If the target precision is higher than the source precision, trailing zeros are appended to the fractional seconds. If the target precision is lower than the source precision, an error is reported.