Timezone data regresses after upgrade
A deploy bumps one direct dependency (`api-client` 2.10 → 2.11) for an unrelated bugfix; tests pass. Two days later, support reports that calendar events and reminders for users in a handful of regions (e.g., parts of Brazil, Egypt) fire one hour wrong, but only for dates after a recent government DST-rule change. Dashboards: no error rate change, no latency change; the only red signal is a user-reported 'reminder accuracy' business metric, regional. Other regions are fine. Context: `api-client` 2.11 tightened a transitive dependency pin and, as a side effect, pulled in an OLDER bundled timezone database (tzdata) than the previous transitive resolution had. Triage and mitigate.
Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.