presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/withTimezone
class DateTimeFunctions:    @ScalarFunction("with_timezone")
    @LiteralParameters("x")
    @SqlType(StandardTypes.TIMESTAMP_WITH_TIME_ZONE)
    public static long withTimezone(ConnectorSession session, @SqlType(StandardTypes.TIMESTAMP) long timestamp, @SqlType("varchar(x)") Slice zoneId)
    {
        TimeZoneKey toTimeZoneKey = getTimeZoneKey(zoneId.toStringUtf8());
        DateTimeZone fromDateTimeZone = session.isLegacyTimestamp() ? getDateTimeZone(session.getTimeZoneKey()) : DateTimeZone.UTC;
        DateTimeZone toDateTimeZone = getDateTimeZone(toTimeZoneKey);
        return packDateTimeWithZone(fromDateTimeZone.getMillisKeepLocal(toDateTimeZone, timestamp), toTimeZoneKey);
    }