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iCal Calendar Subscription

iCal subscriptions allow you to connect read-only calendars from Outlook, public calendars, or any other calendar service that provides an iCal feed. This is perfect for importing schedules you don't control, like work calendars, sports team schedules, or public holiday calendars.

What is an iCal Subscription?

iCal (short for iCalendar) is a standard format for sharing calendar information. When you subscribe to an iCal calendar:

  • Read-only access: Events are pulled from the calendar automatically, but you can't modify them through WhenToMeet
  • Automatic updates: The calendar syncs regularly to fetch new events and updates
  • Universal compatibility: Works with any calendar service that provides an iCal feed URL

How to Find Your iCal Subscription URL

Outlook Calendar

  1. Open Outlook Calendar (web version)
  2. Right-click on the calendar you want to share
  3. Select Settings or Sharing and permissions
  4. Look for Get shareable link or ICS link
  5. Copy the URL (usually starts with https:// and ends with .ics)

Google Calendar (Public Calendars)

  1. Open Google Calendar settings
  2. Select the calendar you want to share
  3. Scroll down to Integrate calendar
  4. Copy the Public address in iCal format

Note: For private Google Calendars with full read-write access, use the native Google Calendar connection instead.

Other Calendar Services

Most calendar services provide an iCal subscription option:

  • Look for Subscribe, Export, or Share options in your calendar settings
  • Find the iCal, ICS, or webcal URL
  • Copy the full URL

Connecting an iCal Subscription

  1. Navigate to the Settings page in WhenToMeet
  2. Under the Calendar section, click Subscribe to iCal Calendar
  3. Paste your subscription URL into the field
  4. The URL can start with either:
    • https:// - Standard secure web URL
    • webcal:// - Calendar-specific protocol (automatically converted to https)
  5. Click Subscribe to connect

WhenToMeet will validate the calendar URL and fetch events to ensure it's working correctly.

Supported URL Formats

  • HTTPS URLs: https://example.com/calendar.ics
  • Webcal URLs: webcal://example.com/calendar.ics (automatically converted)
  • ICS files: URLs pointing to .ics files hosted anywhere

How iCal Subscriptions Work

  1. Initial Connection: When you connect, WhenToMeet fetches all events from the calendar to validate it's accessible
  2. Regular Syncing: Events are automatically synced at regular intervals to stay up-to-date
  3. Conflict Detection: Events from subscribed calendars are used for availability checking, just like your other connected calendars
  4. Date Range Filtering: Only events within your active scheduling period are fetched to optimize performance

Troubleshooting

"Calendar requires authentication" Error

This error means the calendar is private and needs credentials. To fix it:

  1. Click "🔒 Private calendar? Add authentication" in the dialog
  2. Enter your username and password (see Finding Your Credentials above)
  3. Make sure you're using the correct credentials for the calendar service
  4. Try again with authentication enabled

If authentication still fails:

  • Verify your username and password are correct
  • Check if your service requires an app-specific password instead of your main password
  • Ensure the calendar URL is correct and accessible

"Authentication failed" Error

If you've entered credentials but authentication fails:

  • Wrong credentials: Double-check your username and password
  • App-specific password required: Some services (like Microsoft) require app-specific passwords
  • Username format: Try different username formats (email vs. username)
  • Calendar URL: Verify the URL is the actual calendar feed URL, not a web page link

"No events found" Error

If the subscription connects but shows no events:

  • Verify the calendar actually contains events
  • Check that the URL points to a calendar feed (.ics file), not a webpage
  • Some calendars may only provide future events
  • Try accessing the URL directly in your browser to verify it downloads an .ics file

"Connection timeout" Error

If the connection times out:

  • Check that the URL is accessible (try opening it in your browser)
  • The calendar server may be slow or temporarily unavailable
  • Try again in a few minutes
  • Check your internet connection
  • Some self-hosted servers may have rate limiting

Invalid URL Format

  • Make sure the URL is complete and properly formatted
  • Remove any extra spaces or characters
  • Verify the URL starts with https:// or webcal://
  • Ensure the URL ends with .ics or contains a calendar path
  • For NextCloud, make sure you're using the subscription URL, not the web interface URL

Private Calendar Authentication

WhenToMeet supports HTTP Basic Authentication for private calendar subscriptions that require credentials. This allows you to subscribe to private calendars from services like NextCloud, Radicale, or private Outlook calendars.

What is Basic Authentication?

Basic authentication is a standard HTTP authentication method where your username and password are securely encoded and sent with each calendar request. Your credentials are stored encrypted in WhenToMeet's database.

When Do You Need Authentication?

You need authentication when:

  • Private Outlook calendars: Calendars that are not publicly shared
  • NextCloud calendars: Personal calendar subscriptions requiring login
  • Self-hosted calendar servers: Radicale, Baïkal, SOGo, and similar services
  • Private iCal feeds: Any calendar feed that returns a 401 Unauthorized error

Most public calendars (like public Google Calendar feeds or publicly shared Outlook calendars) do NOT need authentication.

How to Use Authentication

  1. In the iCal subscription dialog, click "🔒 Private calendar? Add authentication"
  2. Enter your username (usually your email address or account name)
  3. Enter your password or app-specific password
  4. Click Subscribe to connect

Finding Your Credentials

NextCloud

  • Username: Your NextCloud login email/username
  • Password: Your NextCloud password or an app-specific password
  • URL: Usually https://your-nextcloud.com/remote.php/dav/calendars/USERNAME/CALENDARNAME/?export

Private Outlook Calendar

  • Username: Your Microsoft account email
  • Password: Your Microsoft account password or app-specific password
  • URL: Find it in Outlook Calendar → Settings → Shared calendars → Publish calendar → Get ICS link

Radicale / Baïkal

  • Username: Your calendar server username
  • Password: Your calendar server password
  • URL: Provided by your calendar server (usually ends in .ics or contains /calendars/)

App-Specific Passwords

Many services recommend using app-specific passwords instead of your main account password for security:

  • Microsoft: Generate at account.microsoft.com → Security → App passwords
  • NextCloud: Settings → Security → Create new app password

Privacy & Security

  • Read-only access: iCal subscriptions can only read events, never modify your calendars
  • Encrypted credentials: Authentication credentials are stored encrypted in the database
  • Basic auth support: Standard HTTP Basic Authentication for private calendars
  • SSRF protection: WhenToMeet validates all URLs to prevent access to private networks or internal resources
  • Secure connections: All webcal:// URLs are automatically upgraded to secure https:// connections

Differences from Other Connection Types

iCal vs Google Calendar

  • iCal: Read-only, no OAuth required, works with any public calendar
  • Google: Full read-write access, OAuth authentication, can create events

iCal vs CalDAV

  • iCal: Simple subscription for read-only access, supports optional basic authentication
  • CalDAV: Full bidirectional sync with read-write access, requires CalDAV server support

When to choose iCal:

  • Read-only access is sufficient
  • Calendar provides an iCal/ICS subscription URL
  • Simple setup is preferred
  • Works with Outlook, public calendars, and most calendar services

When to choose CalDAV:

  • You need read-write access (create/edit events)
  • Calendar provider supports CalDAV protocol (iCloud, NextCloud, Fastmail)
  • Full two-way synchronization is required

When to Use iCal

Use iCal subscriptions when:

  • You want to import a public or shared calendar
  • You only need read-only access to check conflicts
  • The calendar is from Outlook or another service without native integration
  • You want a simple setup without OAuth authentication
  • You have a private calendar with basic auth support (see Private Calendar Authentication)

Feature Requirements

iCal subscriptions are available on certain subscription plans. Check the pricing page for details on which features are included in your plan.

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