Cloudflare Workers Date API and Intl.DateTimeFormat: Setting a Default Time Zone for Request Processing

Goal: Achieve consistent regional timestamp handling in a Cloudflare Worker so that all business logic sees times in a chosen zone while the underlying Date object remains UTC.

Constraints: The Workers runtime provides only the ECMAScript Date API, which always returns UTC values and ignores any TZ environment variable; explicit zone conversion must be performed with Intl.DateTimeFormat using an IANA identifier. There is no documented mechanism to set a default time zone for the Worker script, leaving developers to decide whether to apply conversion per request or globally, which can lead to inconsistent handling across services.

Uncertainty: The bundled V8 IANA time‑zone database may lag behind the latest zone changes, potentially causing off‑by‑one‑hour errors for rare historical or future dates, and it is unclear whether a Worker‑wide default zone can be established without repeating the zone argument in every Intl call.

1. Is there a supported way to configure a Worker‑wide default IANA time zone that Intl.DateTimeFormat will use without specifying the zone each time?
2. What patterns are recommended for centrally applying a zone conversion based on request‑origin headers while keeping core Date logic UTC?
3. How does the bundled V8 IANA version affect reliability of zone conversions for edge‑case historical dates, and should developers validate against an external source?