Invalid last_modified value on a timezone other than UTC

[slafon51]

Hello,

We're using kinto with a database using the Europe/Paris timezone, and we've noticed that the bump_timestamp function calculates a value in the future for the last_modified property.
The cause is that the timezone is not taken into account in the as_epoch function. An erroneous timestamp is obtained when the result of the as_epoch function is passed as a parameter to the from_epoch function.

Example :

kinto=# SELECT clock_timestamp(), 
              clock_timestamp()::TIMESTAMP as timestamp,
              from_epoch(as_epoch(clock_timestamp()::TIMESTAMP)) as "timestamp 1 conversion",
              from_epoch(as_epoch(from_epoch(as_epoch(clock_timestamp()::TIMESTAMP)))) as "timestamp 2 conversions";

        clock_timestamp        |         timestamp          | timestamp 1 conversion | timestamp 2 conversions 
-------------------------------+----------------------------+------------------------+-------------------------
 2024-06-14 18:53:38.949726+02 | 2024-06-14 18:53:38.949726 | 2024-06-14 20:53:38.95 | 2024-06-14 22:53:38.95
(1 row)

Best regards.

[leplatrem]

That's probably true indeed.
Are you stuck with the Paris timezone? Can't you do ALTER DATABASE dbname SET TIMEZONE TO UTC;?

Because I don't think we ever supported any other timezone than UTC. We stated in the docs:

https://github.com/Kinto/kinto/blob/5ef3cae12c38cb0441b879b9e2d11707ffb7cc89/docs/configuration/production.rst#database-setup

And that's why we have this check:

kinto/kinto/core/storage/postgresql/__init__.py

Lines 108 to 111 in 5ef3cae

	if timezone != "UTC": # pragma: no cover
	msg = f"Database timezone is not UTC ({timezone})"
	warnings.warn(msg)
	logger.warning(msg)