"Find a time" showing all-day events offset by one day

Steps to reproduce

1. User A creates an all-day event (single or multiple consecutive days).
2. User B attempts to create a new event and adds User A as an invitee.
3. User B uses the "Find a time" feature but User A's all-day event shows as Busy for the PREVIOUS day(s) and not the actual day(s). For example, if User A's event was set for Friday, "Find a time" shows the Thursday as busy. For multiple day events, say Thursday-Friday, the busy time is displayed as Wednesday-Thursday in "Find a time".

Expected behavior

We would expect that the actual day of the other user's event show up in "Find a time".

Actual behavior

"Find a time" shows the other user's even as being scheduled for the previous day(s).

Calendar app version

6.2.1

CalDAV-clients used

No response

Browser

Firefox 148, Chrome 145

Client operating system

Fedora Linux 43

Server operating system

Ubuntu Linux

Web server

Apache

Database engine version

MariaDB

PHP engine version

PHP 8.3

Nextcloud version

33.0

Updated from an older installed version or fresh install

Updated from an older version

List of activated apps

Enabled:
  - activity: 6.0.0-dev.0
  - admin_audit: 1.23.0
  - announcementcenter: 7.3.0
  - app_api: 33.0.0
  - assistant: 3.3.0
  - bruteforcesettings: 6.0.0-dev.0
  - calendar: 6.2.1
  - calendar_resource_management: 0.11.0
  - circles: 33.0.0
  - cloud_federation_api: 1.17.0
  - collectives: 4.0.0
  - comments: 1.23.0
  - contacts: 8.4.0
  - contactsinteraction: 1.14.1
  - dashboard: 7.13.0
  - dav: 1.36.0
  - deck: 1.17.0
  - federatedfilesharing: 1.23.0
  - federation: 1.23.0
  - files: 2.5.0
  - files_accesscontrol: 4.0.0
  - files_downloadlimit: 5.1.0-dev.0
  - files_pdfviewer: 6.0.0-dev.0
  - files_reminders: 1.6.0
  - files_sharing: 1.25.2
  - files_trashbin: 1.23.0
  - files_versions: 1.26.0
  - firstrunwizard: 6.0.0-dev.0
  - forms: 5.2.4
  - groupfolders: 21.0.6
  - impersonate: 4.0.0
  - integration_giphy: 2.2.0
  - integration_openai: 4.3.0
  - logreader: 6.0.0
  - lookup_server_connector: 1.21.0
  - mail: 5.7.1
  - nextcloud_announcements: 5.0.0
  - notes: 4.13.0
  - notifications: 6.0.0
  - notify_push: 1.3.0
  - oauth2: 1.21.0
  - password_policy: 5.0.0-dev.0
  - photos: 6.0.0-dev.0
  - privacy: 5.0.0-dev.0
  - profile: 1.2.0
  - provisioning_api: 1.23.0
  - recommendations: 6.0.0-dev.0
  - related_resources: 4.0.0-dev.0
  - richdocuments: 10.1.0
  - serverinfo: 5.0.0-dev.0
  - settings: 1.16.0
  - sharebymail: 1.23.0
  - spreed: 23.0.1
  - support: 5.0.0
  - survey_client: 5.0.0-dev.0
  - suspicious_login: 11.0.0-dev.0
  - systemtags: 1.23.0
  - tables: 2.0.0
  - tasks: 0.17.1
  - text: 7.0.0-dev.3
  - theming: 2.8.0
  - twofactor_backupcodes: 1.22.0
  - twofactor_totp: 15.0.0-dev.0
  - twofactor_webauthn: 2.6.0
  - updatenotification: 1.23.0
  - user_ldap: 1.24.0
  - user_status: 1.13.0
  - viewer: 6.0.0-dev.0
  - weather_status: 1.13.0
  - webhook_listeners: 1.5.0
  - whiteboard: 1.5.7
  - workflowengine: 2.15.0

Nextcloud configuration

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "192.168.199.199",
            "nextcloud.domain.com"
        ],
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "overwritehost": "nextcloud.domain.com",
        "overwriteprotocol": "https",
        "overwrite.cli.url": "https:\/\/nextcloud.domain.com",
        "dbtype": "mysql",
        "version": "33.0.0.16",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "logtimezone": "UTC",
        "installed": true,
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "filelocking.enabled": "true",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 0,
            "timeout": 0
        },
        "mail_smtpmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauth": true,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "587",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "ldapIgnoreNamingRules": false,
        "ldapProviderFactory": "\\OCA\\User_LDAP\\LDAPProviderFactory",
        "maintenance": false,
        "loglevel": 2,
        "updater.release.channel": "stable",
        "theme": "",
        "mail_sendmailmode": "smtp",
        "mysql.utf8mb4": true,
        "data-fingerprint": "   ",
        "default_phone_region": "TT",
        "auth.storeCryptedPassword": false,
        "app_install_overwrite": [
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        "maintenance_window_start": 22
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}

Web server error log

Log file

Browser log

Additional info

No response

Reproduce the issue in the Calendar app by creating single-day and consecutive all-day events, then using “Find a time” with the event owner as an invitee. Trace the date handling from the Find a time entry point and verify the displayed busy days against the event’s actual days. Done means all-day events appear on the correct dates, including multi-day events, with a regression test covering both cases.