[Bug]: Dashboard shows all-day event in wrong timezone

⚠️ 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

When an all-day event is displayed on the dashboard, the time shown counts down to midnight UTC instead of midnight in the local time zone.

Steps to reproduce

1. Use a different time zone than UTC (in my case, "Europe/Vienna", which is currently UTC+1).
2. Create an all-day event.
3. Wait until after midnight that day.
4. Navigate to the dashboard.
5. The event will be displayed to begin "in ... minutes":

As a consequence, "No more events today" is also wrong.

When navigating to the details of the event, I'm told that the event has already started:

Expected behavior

The dashboard shows the event to start at midnight in my time zone.

Installation method

Community Docker image

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

{
    "system": {
        "debug": false,
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "28.0.1.1",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "versions": "false",
        "maintenance": false,
        "forcessl": true,
        "theme": "",
        "loglevel": 0,
        "trusted_domains": [
            "cloud.rueckgr.at",
            "cloud.rueckgr.at"
        ],
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpmode": "smtp",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.distributed": "\\OC\\Memcache\\Memcached",
        "memcache.locking": "\\OC\\Memcache\\Memcached",
        "memcached_servers": [
            [   
                "host.docker.internal",
                11211
            ]
        ],
        "cache_path": "",
        "trashbin_retention_obligation": "auto",
        "overwrite.cli.url": "https:\/\/cloud.rueckgr.at",
        "mail_smtpauthtype": "PLAIN",
        "updater.release.channel": "stable",
        "mysql.utf8mb4": true,
        "preview_max_memory": 256,
        "app_install_overwrite": [
            "calendar",
            "keeweb",
            "previewgenerator"
        ],
        "default_phone_region": "AT",
        "preview_max_x": 1920,
        "preview_may_y": 1200,
        "mail_smtpauth": 1,
        "mail_sendmailmode": "smtp",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpsecure": "tls"
    }
}

List of activated Apps

Enabled:
  - activity: 2.20.0
  - admin_audit: 1.18.0
  - calendar: 4.6.1
  - circles: 28.0.0-dev
  - cloud_federation_api: 1.11.0
  - contacts: 5.5.0
  - contactsinteraction: 1.9.0
  - dashboard: 7.8.0
  - dav: 1.29.1
  - federatedfilesharing: 1.18.0
  - files: 2.0.0
  - files_pdfviewer: 2.9.0
  - files_reminders: 1.1.0
  - files_sharing: 1.20.0
  - files_trashbin: 1.18.0
  - files_versions: 1.21.0
  - logreader: 2.13.0
  - lookup_server_connector: 1.16.0
  - nextcloud_announcements: 1.17.0
  - notifications: 2.16.0
  - oauth2: 1.16.3
  - password_policy: 1.18.0
  - photos: 2.4.0
  - previewgenerator: 5.4.0
  - privacy: 1.12.0
  - provisioning_api: 1.18.0
  - recommendations: 2.0.0
  - related_resources: 1.3.0
  - serverinfo: 1.18.0
  - settings: 1.10.1
  - support: 1.11.0
  - survey_client: 1.16.0
  - text: 3.9.1
  - theming: 2.3.0
  - twofactor_backupcodes: 1.17.0
  - updatenotification: 1.18.0
  - user_status: 1.8.1
  - viewer: 2.2.0
  - weather_status: 1.8.0
  - workflowengine: 2.10.0
Disabled:
  - bruteforcesettings: 2.8.0 (installed 1.3.0)
  - comments: 1.18.0 (installed 1.8.0)
  - encryption: 2.16.0
  - federation: 1.18.0 (installed 1.8.0)
  - files_external: 1.20.0
  - firstrunwizard: 2.17.0 (installed 1.1)
  - sharebymail: 1.18.0 (installed 1.8.0)
  - suspicious_login: 6.0.0
  - systemtags: 1.18.0 (installed 1.8.0)
  - twofactor_totp: 10.0.0-beta.2
  - user_ldap: 1.19.0

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

No response

Additional info

EDIT: After doing some additional research, I'm unsure whether this issue belongs here or to nextcloud/calendar. Please move it to nextcloud/calendar if necessary.

No source file or test is named in the report. Start by reproducing the dashboard behavior with an all-day event in a non-UTC timezone, then trace the dashboard event display path. Done means the event starts at local midnight and “No more events today” is correct.