CalDAV

CalDAV (RFC 4791) extends WebDAV for managing calendar data on remote servers. It models calendars as WebDAV collections containing iCalendar resources.

Core Concepts

• Calendar collections — WebDAV collections containing iCalendar objects.
• Calendar Home Set — Contains all of a user’s calendars, discovered via the calendar-home-set property.
• Principal URLs — Each user has a principal resource linking to their calendar home set.
• Well-known URL — /.well-known/caldav for service discovery.

HTTP Methods

CalDAV uses standard HTTP methods plus WebDAV extensions:

• GET/PUT/DELETE — Read, create/update, and remove calendar resources.
• PROPFIND — Discover collection properties and list resources.
• REPORT — Calendar-specific queries (e.g., time-range queries via calendar-query).
• MKCALENDAR — Create a new calendar collection.

Calendar Query Example

<C:calendar-query xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:caldav">
  <D:prop>
    <D:getetag/>
    <C:calendar-data/>
  </D:prop>
  <C:filter>
    <C:comp-filter name="VCALENDAR">
      <C:comp-filter name="VEVENT">
        <C:time-range start="20240115T000000Z" end="20240116T000000Z"/>
      </C:comp-filter>
    </C:comp-filter>
  </C:filter>
</C:calendar-query>

Scheduling

CalDAV includes scheduling extensions (RFC 6638) for iTIP-based scheduling, allowing organizers and attendees to exchange invitations, replies, and cancellations through the server.

Sync

The sync-collection report enables efficient synchronization by returning only resources that have changed since the last sync token.