fix(DatePicker): error handling & a11y polish

[aresnik11]

Overview

Adds per-input validation error messages to DatePicker:

• Per-input errors — each DatePickerInput manages its own error, so range mode shows independent messages for the start and end inputs. Typed dates are validated on change and blur; invalid input stays visible until corrected.
• No-shift input layout — the error renders via FormError's absolute variant so the input never changes height: the range-mode arrow stays aligned and no space is reserved when there's no error.
• Calendar offset — the popover shifts down only when it's open and an error exists (via a hasError context flag); closed-state spacing is unchanged.
• Validation util — detects incomplete entries, invalid month/day, date rollover (e.g. Feb 30), and disabled dates.
• Localizable strings — new DatePickerTranslations keys for each error message, with English defaults.

Also adds some calendar/input accessibility refinements:

• Announce full weekday names in calendar headers instead of abbreviations
• Associate the field label with the segment shell via aria-labelledby
• Convert the presentational calendar icon to an IconButton with an openCalendarLabel translation

PR Checklist

• Related to designs:
• Related to JIRA ticket: [ABC-123]
• Version plan added/updated (or not needed)
• I have run this code to verify it works
• This PR includes unit tests for the code change
• This PR includes testing instructions tests for the code change
• The alpha package of this PR is passing end-to-end tests in all relevant Codecademy repositories

Testing Instructions

Single mode

1. Type 2/30/2024 and blur → shows "February does not have 30 days".
2. Correct to 2/28/2024 → error clears and the date commits.
3. Open/close the calendar several times → spacing above it stays consistent.
4. With a disableDate prop, type a disabled date → shows "This date is not available".

Range mode

5. Start input: type 2/30/2024 → error appears under the start input only.
6. End input: type an invalid date → a separate error appears under the end input.
7. Confirm the arrow separator does not move when errors appear/disappear.
8. Correct the start date → start error clears while the end error (if any) remains.

Calendar + spacing

9. Open the calendar with no error and note the spacing above it.
10. Trigger an error while it's open → the calendar shifts down so the error is visible.
11. Close and reopen → spacing matches step 9 (no drift).

Accessibility

12. Each error announces via its role="alert" region; start/end errors announce independently.
13. aria-invalid toggles on each input as its error state changes.
14. Calendar weekday headers announce full weekday names (e.g. "Monday").

PR Links and Envs

Repository	PR Link
Monolith	Monolith PR
Mono	Mono PR

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 7f941b4

---

☁️ Nx Cloud last updated this comment at 2026-07-13 21:11:33 UTC

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 81bac52

---

☁️ Nx Cloud last updated this comment at 2026-07-07 19:14:44 UTC

[codecov]

Codecov Report

❌ Patch coverage is 30.18868% with 74 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.06%. Comparing base (b578661) to head (7f941b4).
⚠️ Report is 5 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...src/DatePicker/DatePickerInput/utils/validation.ts	15.62%	54 Missing ⚠️
...ges/gamut/src/DatePicker/DatePickerInput/index.tsx	48.71%	20 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3395      +/-   ##
==========================================
- Coverage   90.55%   89.06%   -1.50%     
==========================================
  Files         398      271     -127     
  Lines        6586     5761     -825     
  Branches     2131     1944     -187     
==========================================
- Hits         5964     5131     -833     
- Misses        613      621       +8     
  Partials        9        9              

Flag	Coverage Δ
main	?
pull-request	89.06% <30.18%> (?)

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[codecademydev]

📬 Published Alpha Packages:

Package	Version	npm	Diff
@codecademy/gamut	72.2.3-alpha.303f64.0	npm	diff
@codecademy/gamut-icons	9.57.10-alpha.303f64.0	npm	diff
@codecademy/gamut-illustrations	0.58.16-alpha.303f64.0	npm	diff
@codecademy/gamut-kit	3.0.7-alpha.303f64.0	npm	diff
@codecademy/gamut-patterns	0.10.35-alpha.303f64.0	npm	diff
@codecademy/gamut-styles	20.0.3-alpha.303f64.0	npm	diff
@codecademy/gamut-tests	6.0.6-alpha.303f64.0	npm	diff
@codecademy/variance	0.26.2-alpha.303f64.0	npm	diff
eslint-plugin-gamut	2.4.4-alpha.303f64.0	npm	diff

[github-actions]

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