Microsoft 365 Calendar Integration for Nextcloud

Integrate Microsoft 365 users into the Nextcloud Calendar with attendee search and free/busy availability.

Features

• Attendee Search — Search Microsoft 365 users when adding attendees to calendar events
• Free/Busy — View availability of MS365 users directly in Nextcloud Calendar
• Reply Notifications — Get notified when attendees accept, decline or tentatively accept invitations
• OAuth2 with PKCE — Secure per-user authentication with Microsoft Entra ID

Requirements

• Nextcloud 28–33
• PHP 8.2+
• An App Registration in Microsoft Entra ID (Azure AD)

Installation

1. Clone or download this repository into your Nextcloud apps/ directory:

   cd /var/www/nextcloud/apps
   git clone https://github.com/sara-nl/nextcloud-microsoft-calender.git nc_ms365_calendar

2. Install dependencies and build the frontend:

   cd nc_ms365_calendar
   composer install --no-dev
   npm install
   npm run build

3. Enable the app:

   occ app:enable nc_ms365_calendar

Microsoft Entra ID Setup

1. Create an App Registration

• Go to Azure Portal → App registrations → New registration
• Name: e.g. "Nextcloud Calendar Integration"
• Supported account types: Single tenant (your organization)
• Redirect URI: Web → https://your-nextcloud.com/apps/nc_ms365_calendar/oauth/callback

2. Configure API Permissions

Add the following Delegated permissions under Microsoft Graph:

Permission	Purpose	Admin Consent
User.ReadBasic.All	Search users	Required
People.Read	Relevant contacts	No
Calendars.Read	Free/busy information	No
Calendars.Read.Shared	Shared calendar free/busy	No
offline_access	Refresh tokens	No

Click Grant admin consent after adding permissions.

3. Create a Client Secret

• Go to Certificates & secrets → New client secret
• Copy the secret value (it's only shown once)

4. Note Your IDs

You'll need:

• Tenant ID — found on the Overview page of your App Registration
• Client ID (Application ID) — found on the Overview page
• Client Secret — from step 3

Nextcloud Configuration

Admin Settings

Go to Administration settings → Microsoft 365 Calendar Integration and enter:

• Tenant ID
• Client ID
• Client Secret
• Cache TTL — How long search results are cached (default: 300s)
• Reply Notifications — Send notifications when attendees respond to invitations (toggle on/off)

User Connection

Each user connects their own Microsoft 365 account:

1. Go to Personal settings → Microsoft 365 Calendar
2. Click Connect to Microsoft 365
3. Sign in with your Microsoft account and grant permissions

How It Works

Attendee Search

When a user searches for attendees in the Calendar app, the app queries the Microsoft Graph API using multiple strategies:

1. People API — Finds frequently contacted people
2. Users API — Searches by display name and email
3. Results are merged, deduplicated, and cached (5-minute TTL)

Free/Busy

The app registers a Sabre DAV plugin that intercepts CalDAV free/busy requests:

1. Identifies external attendees (not in Nextcloud)
2. Queries Microsoft Graph /me/calendar/getSchedule
3. Merges MS365 availability with Nextcloud's response
4. Works transparently with any CalDAV client (Apple Calendar, Thunderbird, etc.)

Status mapping:

MS365 Status	CalDAV Status
busy	BUSY
tentative	BUSY-TENTATIVE
oof (Out of Office)	BUSY-UNAVAILABLE
workingElsewhere	BUSY-TENTATIVE

Reply Notifications

When enabled in admin settings, the app monitors calendar event updates for PARTSTAT changes (accept/decline/tentative) and sends Nextcloud notifications to the event organizer.

Development

# Install dependencies
composer install
npm install

# Build frontend
npm run build

# Watch mode
npm run dev

# Run tests
./vendor/bin/phpunit

License

AGPL-3.0-or-later