presto-spi/src/main/java/io/prestosql/spi/type/DateTimeEncoding.java/DateTimeEncoding/unpackZoneKey
class DateTimeEncoding:    public static TimeZoneKey unpackZoneKey(long dateTimeWithTimeZone)
    {
        return getTimeZoneKey((short) (dateTimeWithTimeZone & TIME_ZONE_MASK));
    }