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# Technical Advisory 56116

Publication date: October 29, 2020

## Description

All currently-released versions of the Go runtime [incorrectly interpret](https://github.com/golang/go/issues/42138) the daylight-savings flag in "slim" versions of zoneinfo that are used by some OS distributions. This can result in incorrect local date-time calculations for any version of CockroachDB that is running on an OS image that distributes "slim" zoneinfo files.

* Users of official CockroachDB Docker images are not affected.
* Users of our reference Kubernetes configurations are not affected.
* Users of CockroachCloud are not affected.

## Mitigation

Execute the following SQL statement to determine if your cluster is affected:

```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}}
SET TIME ZONE UTC; -- The default for cockroach sql
SELECT '2020-10-29 15:30'::TIMESTAMPTZ AT TIME ZONE 'Europe/Berlin' AT TIME ZONE 'UTC';
```

If a value other than `2020-10-29 16:30:00+00:00` is returned, you are affected by this Go runtime bug and should perform the following remediation:

* Download [zoneinfo.zip 2020a](https://github.com/golang/go/tree/5c9a8c0761ae643828a4526db764ac7a50a1a24d/lib/time) from the golang development tree to each CockroachDB node.
* Perform a rolling restart of all CockroachDB processes, setting the `ZONEINFO` environment variable to the path of the `zoneinfo.zip` file.
* Confirm the fix by executing the above SQL statement.

## Impact

Any clusters impacted by this issue may produce incorrect results when performing date/time calculations that involve values in timezones and time periods for which daylight savings are in effect.

Questions about any technical alert can be directed to our [support team](https://support.cockroachlabs.com/).