Bugfix: Fix correct deadline/start date validation in job creation form

[CelineLahnor]

Checklist

General

• I tested all changes and their related features with all corresponding user types.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Client

• Important: I implemented the changes with a very good performance, prevented too many (unnecessary) REST calls and made sure the UI is responsive, even with large data (e.g. using paging).
• I strictly followed the principle of data economy for all client-server REST calls.
• I strictly followed the client coding and design guidelines.
• I added multiple integration tests (Vitest) related to the features (with a high test coverage), while following the client test guidelines.
• I documented the TypeScript code using JSDoc style.
• I added multiple screenshots/screencasts of my UI changes.

Motivation and Context

Closes #1487

Description

This PR prevents invalid date combinations in the professor job creation form by enforcing that the start date must be the same day as or later than the application deadline.

Changes

• added client-side validation so startDate must be the same day as or later than applicationDeadline
• disabled invalid dates in both date pickers depending on which date is selected first
• highlighted the reference date in the datepicker with a tooltip
• extracted shared local date parsing logic
• moved datepicker styling to Tailwind
• added some small client tests for this behavior

Steps for Testing

1. Log in as Professor
2. Create a new position draft
3. Select a Start Date
4. Open the Deadline Date Picker and verify that the User can not pick a Deadline after the Start Date
5. Verify the Start Date is highlighted within the Date Picker
6. After selecting a Deadline verify this is also highlighted in the Date Picker for the Start Date
7. Verify that the User can not pick a Start Date before the Deadline

Review Progress

Code Review

• Code Review 1

Manual Tests

• Test 1

Screenshots

Bildschirmaufnahme.2026-04-18.um.15.32.32.mov

I also updated the job creation form so the start date picker appears on the left and the application deadline picker on the right, matching the intended UI order.

Test Coverage

Client

Class/File	Line Coverage	Lines	Expects	Ratio
slot-creation-form.component.ts	0.00%	342	40	11.7
job-creation-form.component.ts	63.77%	1116	137	12.3
datepicker.component.ts	100.00%	162	39	24.1
saving-states.ts	100.00%	7	?	?
date-time.util.ts	45.16%	57	?	?
date-order-validator.ts	90.90%	18	?	?

Last updated: 2026-04-19 15:30:23 UTC

[codacy-production]

Not up to standards ⛔

🔴 Issues 1 medium

Alerts:
⚠ 1 issue (≤ 0 issues of at least minor severity)

Results:
1 new issue

Category	Results
Complexity	1 medium

View in Codacy

🟢 Metrics 33 complexity

Metric	Results
Complexity	33

View in Codacy

_{TIP This summary will be updated as you push new changes. Give us feedback}

[Copilot]

Pull request overview

This PR fixes invalid date combinations in the professor job creation form by ensuring the position start date cannot be earlier than the application deadline, and by improving the datepicker UX to guide correct selection.

Changes:

• Add a shared form-group validator to enforce startDate >= applicationDeadline.
• Derive datepicker min/max bounds from the opposite selected date and visually highlight the reference date with a tooltip.
• Extract shared local date parsing logic and expand Vitest coverage for the new behavior.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/main/webapp/app/job/job-creation-form/job-creation-form.component.ts	Adds date-order validation, computed min/max bounds for date pickers, and blocks autosave when date order is invalid.
src/main/webapp/app/job/job-creation-form/job-creation-form.component.html	Wires new min/max bounds and highlighted reference date tooltips into both date pickers.
src/main/webapp/app/shared/validators/date-order-validator.ts	Introduces a reusable cross-field validator for ISO local date strings.
src/main/webapp/app/shared/util/date-time.util.ts	Adds parseLocalDateString for timezone-safe parsing of YYYY-MM-DD into local-midnight Date.
src/main/webapp/app/shared/components/atoms/datepicker/datepicker.component.ts	Uses shared local date parsing and adds highlighted-day detection.
src/main/webapp/app/shared/components/atoms/datepicker/datepicker.component.html	Moves styling to Tailwind and renders the highlighted reference day with a tooltip.
src/main/webapp/app/shared/components/atoms/datepicker/datepicker.component.scss	Removes SCSS styling now replaced by Tailwind selectors.
src/main/webapp/i18n/en/job.json	Updates placeholder text and adds labels for highlighted reference dates.
src/main/webapp/i18n/de/job.json	Updates placeholder text and adds labels for highlighted reference dates.
src/test/webapp/app/job/job-creation-form/job-creation-form.component.spec.ts	Adds tests for date-order validity and derived datepicker bounds.
src/test/webapp/app/shared/components/atoms/datepicker/datepicker.component.spec.ts	Adds a test for highlighted reference date detection.

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