Every organization has a single timezone. It sets when the daily dependency-change digest is sent (09:00 local) and formats timestamps in those emails. It is also shown on the Organization settings page. See Help center → Dependency change digests (Dependency change digests).
New organizations default to Europe/Copenhagen when the browser zone is missing or invalid. During onboarding, a searchable timezone picker is preset from your browser, so most teams confirm it once and never need to change it.
Changing it
Open Organization settings and use the searchable timezone picker to find a timezone by city or region name, then save.