[Bug]: Inconsistency in date format in placeholder (in Availability)

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

I use uk_UA locale which supposed the date format dd.mm.yyyy. However, in separate parts of the webUI I see the date format dd/mm/yyyy.

Steps to reproduce

1. Either select forcedly or give option to users to select the locale uk_UA (Ukraine)
2. Observe, that the default date is in the format dd.mm.yyyy
3. Go to the page Availaibility and observe that the date placeholder is shown in the format dd/mm/yyyy

4. Test the tables app, which also shows the date placeholder shown in dd/mm/yyyy.

Expected behavior

The date format should inherit the selected locale.

Installation method

Community Web installer on a VPS or web space

Nextcloud Server version

28

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

MariaDB

Is this bug present after an update or on a fresh install?

Upgraded to a MAJOR version (ex. 22 to 23)

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

The bug has appeared after upgrade from 27.1.9 to 28.0.5.

Start at the Availability page and compare its date placeholder with the locale-aware date shown elsewhere in the webUI; the issue also identifies the Tables app as another affected entry point. Reproduce with the uk_UA locale and verify that both placeholders inherit the selected locale's date format.