Release Incident Playbook

Encoding or timezone shift: symptoms, cause, and the test that catches it

Stored timestamps or strings are shifted or corrupted after a driver, locale or timezone change.

Encoding or timezone shift is documented by 2 accepted public reports from 2 organisations, 1 of them published in the last 5 years.

  • Likelihood: not published (1 public report in 5 years)
  • Impact: high (2 of 2 reports: data)

2 public reports · verified 2026-10-22

Symptoms

User-visible

  • Users with a custom account timezone get wrong results from timezone-based calculations, for about two hours on one warehouse connection type.[1]
  • The same wrong results return for 30 minutes on a second warehouse connection type after the first one is fixed.[1]
  • Customer filter queries return incorrect results.[1]
  • Notes added through the web dashboard display a time 4 hours in the future.[2]

Monitoring-visible

  • An internal backend health test that checks timezone handling fails for the affected warehouse connection, 32 minutes after the production change.[1]
  • Customers reported wrong times on dashboard notes, and a customer reported the wrong results on the second warehouse connection type.[2][1]

Root causes

  1. stage: code A code change to a backend component stopped setting the session timezone in the drivers that connect to customer data warehouses, so the account timezone was not passed between components.[1]
  2. stage: config An infrastructure change to how the dashboard module is served left the timezone configuration variable set to NULL, so new notes were stored against the wrong offset.[2]
  3. stage: release-process The exit criteria for the infrastructure change did not check that timestamps were recorded in the right timezone, so the change passed testing with no application error.[2]

Public examples

  1. [1]Sigma Computing, 2023-10-06. A backend code change stopped timezones from being set in the drivers Sigma uses to connect to customer data warehouses, so users with a custom account timezone saw incorrect results for timezone-based calculations on Snowflake and later on Databricks. primary Postmortem for Aug 10th, 2023: Incorrect results for timezone-based calculations
  2. [2]ServiceChannel, 2020-04-08. An infrastructure change to how the ServiceChannel Dashboard module is served left the timezone configuration variable set to NULL, so Work Order Notes were recorded four hours into the future and 3,178 notes needed a retroactive timezone correction. primary ServiceChannel Status - Incorrect Work Order Timezone

Test classes that catch it

Test classStageLimitationBasis
Configuration and environment testspre-deployA configuration test that only checks the timezone variable on the serving layer misses a code change that drops the timezone inside a warehouse driver connection.cited in [2]
Integration testspre-deployAn integration test against one warehouse connection type misses the same fault on a second connection type, and it misses a timezone variable left NULL only in the changed serving layer.by design analysis
Synthetic monitoringpost-deployA synthetic check that runs as an account in the default timezone never sees the wrong results, because only accounts with a custom timezone are affected.by design analysis

Risk

  • Likelihood: not published (1 public report in 5 years)
  • Impact: high (2 of 2 reports: data)
Counts behind the grades
Accepted public reports2
Published in the last 5 years1
Impact stated: data2

How the grades are computed

Pre-release checklist

  • PR-01
  • PR-02
  • PR-03
  • PR-04
  • PR-05
  • PR-06

First 30 minutes

  • FM-01
  • FM-02
  • FM-03
  • FM-04
  • FM-05
  • FM-06

Download the checklist

What catches this: catalogue entries

Listed because their own documentation or site names configuration and environment tests, integration tests, synthetic monitoring on the verification date. Alphabetical. Not a recommendation.

Tools whose documentation names these test classes

Providers whose site names these test classes

Only on this page

Encoding or timezone shift sits in the data migrations group, yet neither report [1] nor report [2] involves a schema migration. One fault entered through a code change in a warehouse driver connection [1]. The other entered through an infrastructure change that left the timezone configuration variable NULL [2].

Because neither fault changes the schema, migration tests never run against it. One report counts 3,178 notes that needed a retroactive timezone correction after customers reported the wrong times [2].

Questions

What causes encoding or timezone shift?

In the 2 public reports, one cause is a code change that stopped setting the timezone in warehouse drivers [1]. The other is an infrastructure change that left the timezone configuration variable NULL [2].

What are the symptoms of encoding or timezone shift?

Users see wrong results from timezone-based calculations and notes stamped 4 hours in the future. The test suite can show no application error while the wrong timestamps are written [2].

Why did tests not catch encoding or timezone shift?

One report states that the test exit criteria did not check that timestamps were recorded in the right timezone [2]. Only accounts with a custom timezone saw wrong results in the other report [1].

Which test class catches encoding or timezone shift, and what does it miss?

Configuration tests carry a cited basis from one report [2], while integration tests and synthetic monitoring are listed by design. A configuration test on the serving layer misses a timezone dropped inside a warehouse driver.

How long did it take to detect encoding or timezone shift in the public reports?

A failing internal backend health test flagged one case 32 minutes after the production change [1]. The other cases were reported by customers.

Should a team roll back or fix forward when encoding or timezone shift happens?

Both reports rolled the change back [1] [2]. Report [2] then applied a retroactive timezone update to 3,178 notes. Checklist item FM-05 applies the correction only after the rollback stops new wrong writes.

Release Incident Playbook (2026). Encoding or timezone shift: symptoms, cause, and the test that catches it, content version 1.0.0. https://releasefailures.com/incidents/encoding-or-timezone-shift/. Accessed 2026-10-21.