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docs: document TZ=UTC default for wrangler dev local runtime#30527

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pbd/miniflare-tz-utc
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docs: document TZ=UTC default for wrangler dev local runtime#30527
petebacondarwin wants to merge 1 commit intoproductionfrom
pbd/miniflare-tz-utc

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@petebacondarwin petebacondarwin commented May 2, 2026

Summary

Documents the new TZ=UTC default for the local Workers runtime, introduced in cloudflare/workers-sdk#13776 (closes cloudflare/workers-sdk#8106).

Cloudflare's production runtime runs Workers with TZ=UTC, but Miniflare previously inherited the host machine's timezone, causing dev/prod drift in Date and Intl behaviour. Local development now matches production by default — this PR updates the docs to reflect that.

Two small additions:

Documentation checklist

  • Is there a changelog entry? — N/A; this documents an existing in-flight change to local dev behaviour. The workers-sdk PR will produce a Wrangler/Miniflare changelog entry.
  • The change adheres to the documentation style guide.
  • If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes. — N/A; not a new page.
  • Files which have changed name or location have been allocated redirects. — N/A; no renames or moves.

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Local Workers development now runs with TZ=UTC to match the production
Cloudflare runtime (cloudflare/workers-sdk#13776, closes
cloudflare/workers-sdk#8106). Document the new default in two places:

- Add a bullet to the Defaults list on the Development & testing page.
- Add a Note callout under `wrangler dev` on the Workers commands page.
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github-actions Bot commented May 2, 2026

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern Owners
/src/content/docs/workers/ @cloudflare/workers-docs, @GregBrimble, @irvinebroque, @mikenomitch, @korinne, @WalshyDev, @cloudflare/deploy-config, @cloudflare/pcx-technical-writing, @cloudflare/product-owners, @cloudflare/wrangler, @mattietk, @cloudflare/dev-plat-leads
/src/content/docs/workers/wrangler/ @cloudflare/wrangler, @irvinebroque, @cloudflare/pcx-technical-writing, @cloudflare/product-owners

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

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[miniflare]: Set TZ=UTC for wrangler dev

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