fix(date-panel): fix date selection off-by-one day when clicking dates( #4138)

[Georgyhongbo]

The modelValue watcher in date-panel incorrectly used getUTCDate() + 1 which caused a double timezone correction, resulting in the selected date being offset by one day. Changed to use getDate() which gives the correct local date value, consistent with how date-range and month-range components handle the same logic.

PR Checklist

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• The commit message follows our Commit Message Guidelines
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PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

When clicking a date in the DatePanel component, the wrong date is selected. For example, clicking "15" first selects "16". A second click on "15" is required to correctly select it. The bug occurs because the modelValue watcher applies a double timezone correction (val - localOffset plus getUTCDate() + 1), which shifts the date forward by one day.

Issue Number: N/A

What is the new behavior?

Clicking any date in DatePanel selects the correct date immediately, with no off-by-one error.

Does this PR introduce a breaking change?

• Yes
• No

Other information

Only one line changed in packages/renderless/src/date-panel/vue.ts. The fix aligns with how date-range and month-range already handle the same logic using getDate() instead of getUTCDate() + 1.

Summary by CodeRabbit

• Bug Fixes
  • Improved date selection normalization across time zones.
  • Fixed displayed dates that could shift by one day for certain time zone offsets.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between e5e921b and f9d9f80.

📒 Files selected for processing (1)

• packages/renderless/src/date-panel/vue.ts

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Walkthrough

The date-panel modelValue watcher now normalizes incoming dates using the local day component instead of a UTC-derived day.

Changes

Date normalization

Layer / File(s)	Summary
Normalize incoming model values packages/renderless/src/date-panel/vue.ts	The modelValue watcher passes newVal.getDate() to modifyDate when updating state.date and state.value.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• opentiny/tiny-vue#4261: Updates the same date-panel watcher for local timezone normalization.

Poem

A bunny hops through dates so bright,
No UTC twist can steal the night.
The local day now leads the way,
Keeping calendars right each day.
Carrots cheer the fix—hooray! 🐇

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main bug fix in date-panel and is specific enough for history scanning.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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