presto-main/src/main/java/io/prestosql/operator/scalar/DateTimeFunctions.java/DateTimeFunctions/toISO8601FromTimestampWithTimeZone
class DateTimeFunctions:    @ScalarFunction("to_iso8601")
    @SqlType("varchar(35)")
    // YYYY-MM-DDTHH:MM:SS.mmm+HH:MM is a standard notation, and it requires 29 characters.
    // However extended notation with format ±(Y)+-MM-DDTHH:MM:SS.mmm+HH:MM is also acceptable and as
    // the maximum year represented by 64bits timestamp is ~584944387 it may require up to 35 characters.
    public static Slice toISO8601FromTimestampWithTimeZone(@SqlType(StandardTypes.TIMESTAMP_WITH_TIME_ZONE) long timestampWithTimeZone)
    {
        long millisUtc = unpackMillisUtc(timestampWithTimeZone);
        DateTimeFormatter formatter = ISODateTimeFormat.dateTime()
                .withChronology(getChronology(unpackZoneKey(timestampWithTimeZone)));
        return utf8Slice(formatter.print(millisUtc));
    }