bigquery timestamp

[tiboun]

I create this issue in order to discuss about timestamp handling in bigquery. Even if output is similar to bigquery in unit tests, the java timestamp doesn't seems to be in phase between Bigquery's timestamp and duckdb's timestamp.

Bigquery java timestamp is:

Whereas duckdb's timestamp is:

We can notice that the timezone generated by the toString method of Timestamp is different.

If we format the timestamp as UTC:

![image](https://github.com/user-attachments/assets/1b877895-8bb8-42ee-8823-e1dafcaac0a2)

We get the expected output.

If we apply the same to DuckDB's output, we get:

Please check the example below:

SELECT GENERATE_TIMESTAMP_ARRAY(start_timestamp, end_timestamp, INTERVAL 1 HOUR)
           AS timestamp_array
FROM
    (SELECT
         TIMESTAMP '2016-10-05 00:00:00' AS start_timestamp,
         TIMESTAMP '2016-10-05 02:00:00' AS end_timestamp
     UNION ALL
     SELECT
         TIMESTAMP '2016-10-05 12:00:00' AS start_timestamp,
         TIMESTAMP '2016-10-05 14:00:00' AS end_timestamp
     UNION ALL
     SELECT
         TIMESTAMP '2016-10-05 23:59:00' AS start_timestamp,
         TIMESTAMP '2016-10-06 01:59:00' AS end_timestamp);

Obtained:

SELECT
	Generate_Series(start_timestamp::TIMESTAMP,
	end_timestamp::TIMESTAMP,
	INTERVAL 1 HOUR::INTERVAL) AS timestamp_array
FROM
	(
	SELECT
		TIMESTAMP '2016-10-05 00:00:00' AS start_timestamp,
		TIMESTAMP '2016-10-05 02:00:00' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMP '2016-10-05 12:00:00' AS start_timestamp,
		TIMESTAMP '2016-10-05 14:00:00' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMP '2016-10-05 23:59:00' AS start_timestamp,
		TIMESTAMP '2016-10-06 01:59:00' AS end_timestamp)

But expected one of :

SELECT
	Generate_Series(start_timestamp,
	end_timestamp,
	INTERVAL 1 HOUR::INTERVAL) AS timestamp_array
FROM
	(
	SELECT
		TIMESTAMPTZ '2016-10-05 00:00:00+00' AS start_timestamp,
		TIMESTAMPTZ '2016-10-05 02:00:00+00' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMPTZ '2016-10-05 12:00:00+00' AS start_timestamp,
		TIMESTAMPTZ '2016-10-05 14:00:00+00' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMPTZ '2016-10-05 23:59:00+00' AS start_timestamp,
		TIMESTAMPTZ '2016-10-06 01:59:00+00' AS end_timestamp);

SELECT
	Generate_Series(start_timestamp,
	end_timestamp,
	INTERVAL 1 HOUR::INTERVAL) AS timestamp_array
FROM
	(
	SELECT
		TIMESTAMP '2016-10-05 00:00:00' AT TIME ZONE 'UTC' AS start_timestamp,
		TIMESTAMP '2016-10-05 02:00:00' AT TIME ZONE 'UTC' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMP '2016-10-05 12:00:00' AT TIME ZONE 'UTC' AS start_timestamp,
		TIMESTAMP '2016-10-05 14:00:00' AT TIME ZONE 'UTC' AS end_timestamp
UNION ALL
	SELECT
		TIMESTAMP '2016-10-05 23:59:00' AT TIME ZONE 'UTC' AS start_timestamp,
		TIMESTAMP '2016-10-06 01:59:00' AT TIME ZONE 'UTC' AS end_timestamp)

This is because bigquery timestamp is with timezone and when not defined, it sets to UTC.
Getting epoch from timestamp results in a different output value when no timestamp is specified.

Serializing