Fix RelativeTime hydration across time zones - #8330
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🦋 Changeset detectedLatest commit: f80c0da The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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Pull request overview
Updates RelativeTime to render its fallback date deterministically during SSR/hydration by formatting the fallback in UTC, preventing hydration mismatches when server and client local time zones differ.
Changes:
- Add
timeZone: 'UTC'to the fallbacktoLocaleDateStringformatting options. - Add a hydration regression test intended to catch mismatches when server/client time zones differ.
- Add a patch changeset for
@primer/react.
Show a summary per file
| File | Description |
|---|---|
| packages/react/src/RelativeTime/RelativeTime.tsx | Forces fallback date formatting to UTC for consistent SSR/client output. |
| packages/react/src/RelativeTime/RelativeTime.test.tsx | Adds a hydration regression test for differing server/client time zones. |
| .changeset/quiet-times-agree.md | Publishes the change as a patch release entry. |
Review details
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- Files reviewed: 3/3 changed files
- Comments generated: 2
- Review effort level: Lite
| const localeOptions: Intl.DateTimeFormatOptions = { | ||
| month: 'short', | ||
| day: 'numeric', | ||
| year: 'numeric', | ||
| timeZone: 'UTC', | ||
| } satisfies Intl.DateTimeFormatOptions |
| const toLocaleDateStringSpy = vi.spyOn(Date.prototype, 'toLocaleDateString').mockReturnValue('Mar 7, 2024') | ||
| const container = document.createElement('div') | ||
| container.innerHTML = renderToString(relativeTime) | ||
| document.body.appendChild(container) | ||
|
|
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| toLocaleDateStringSpy.mockImplementation((_locales, options) => | ||
| options?.timeZone === 'UTC' ? 'Mar 7, 2024' : 'Mar 6, 2024', | ||
| ) |
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Integration test results from github/github-ui PR:
All checks passed! |
Closes #
Prevent
RelativeTimefallback text from differing between server and client when they use different local time zones. The fallback now formats dates in UTC, matching deterministically across SSR and hydration.Changelog
New
None.
Changed
RelativeTimeuses UTC when rendering its fallback date.Removed
None.
Rollout strategy
Testing & Reviewing
node node_modules/vitest/vitest.mjs run --root . --project @primer/react packages/react/src/RelativeTime/RelativeTime.test.tsx