presto-iceberg/src/main/java/io/prestosql/plugin/iceberg/PartitionTransforms.java/PartitionTransforms/bucketTimestampWithTimeZone
class PartitionTransforms:    private static Block bucketTimestampWithTimeZone(Block block, int count)
    {
        return bucketBlock(block, count, position -> {
            long value = unpackMillisUtc(TIMESTAMP_WITH_TIME_ZONE.getLong(block, position));
            return bucketHash(MILLISECONDS.toMicros(value));
        });
    }