The timeZone field in the Preference Details field group usually needs to be populated with a valid IANA timezone value (for example America/New_York or Europe/London). In Adobe Experience Platform, this field is normally populated directly from the source data rather than automatically calculated.
At the moment there isn’t a built-in computed attribute that converts a city or postal code into a timezone inside the platform. If you want to derive it automatically, the common approach is to resolve the timezone before the data is ingested. For example, you can enrich the dataset using a lookup table or an external service that maps location data (city, postal code, or coordinates) to a timezone, and then pass that value into the timeZone attribute during ingestion.
Another option some teams use is to maintain a small reference dataset with postal codes or regions mapped to their timezone and join it during data preparation. This ensures the field is populated consistently and avoids relying on runtime calculations.