Cloudflare Workers Intl.DateTimeFormat ambiguity during DST transitions

Cloudflare Workers utilizes the V8 ICU implementation, allowing Intl.DateTimeFormat to accept IANA time zone names for regional date conversion. While this supports standard formatting, the Date object remains anchored to UTC timestamps.

A technical uncertainty arises during Daylight Saving Time (DST) transitions, specifically when a local time occurs twice (the "fall back" overlap). Because the runtime does not provide a mechanism to resolve these ambiguous local times automatically, developers must determine how to handle the offset transition without introducing heavy external tzdata libraries that increase cold-start latency.

Implementation Constraints

• The environment is stateless and lacks a system-configured local time zone.
• Intl formatters default to UTC if the timeZone option is omitted.
• Bundling full Node.js-compatible date libraries may exceed script size limits or fail due to missing fs or process APIs.

How does the Workers runtime handle the resolution of ambiguous local timestamps during a DST overlap when using Intl.DateTimeFormat? Is there a native way to specify the preferred offset (standard vs. daylight) for a specific IANA zone without external dependencies?