presto-spi/src/main/java/io/prestosql/spi/type/SqlTimestamp.java/SqlTimestamp/toString
class SqlTimestamp:    @JsonValue
    @Override
    public String toString()
    {
        ZoneId zoneId = sessionTimeZoneKey
                .map(TimeZoneKey::getId)
                .map(ZoneId::of)
                .orElse(ZoneOffset.UTC);

        return Instant.ofEpochMilli(millis)
                .atZone(zoneId)
                .format(JSON_FORMATTER);
    }