CalDAV is a project for a standard protocol that makes it possible to access calendar files via WebDAV.

The CalDAV specification was submitted by Lisa Dusseault as a draft to the Internet Engineering Task Force ( IETF) for the first time in 2003 and quickly gained the support of some manufacturer of calendar software. In January 2005, the first time was a test between two servers and three clients; this worked successfully. CalDAV does not have an IETF working group, but the developers have still published it as an IETF standard RFC 4791 Calendaring Extensions to WebDAV ( CalDAV ). CalDAV is designed for implementation in any calendar software. Here, the CalDAV protocol manages the access to the data according to pre-defined access rules. It was designed as an open standard, to support a platform independent usage.

The task of CalDAV is to manage events such as meetings, assemblies and Frei-/Belegt-Zeiten and publish via HTTP. Each event is represented in the iCalendar format. Accordingly, any web browser display a downloaded event. The data is managed and synced as files in a WebDAV environment. The CalDAV protocol complements the HTTP (RFC 2616) and the WebDAV protocol (RFC 2518) to perform the functions WebDAV Access Control (RFC 3744), iCalendar evaluation functions (RFC 5545) and some other special calendar extensions such as the write lock, other users, the offset in the file write mode, the transmission of free dates, and the administration of recurring events. With this functionality, a user can synchronize its calendar with a CalDAV server and share it with multiple devices or other users. Thus, the protocol supports the free publication of the calendar.

Some developers have the complexity of CalDAV criticized because it is difficult to implement and may lead to implementation errors in different calendar management applications, which in turn lead to incompatibilities.

Current CalDAV information can be found on the CalDAV website.


The example is based on the RFC 4791 and was taken from the Linux magazine:


REPORT / bernard / work / HTTP/1.1 Host: Depth: 1 Content-Type: application / xml; charset = "utf -8" Content-Length: xxxx < / C: free- busy- query> Answer:

HTTP/1.1 200 OK Date: Sat, November 11, 2006 09:32:12 GMT Content-Type: text / calendar Content-Length: xxxx BEGIN: VCALENDAR VERSION: 2.0 PRODID :-/ / Example Corp.. / / CalDAV Server / / EN BEGIN: VFREEBUSY DTSTAMP: 20050125T090000Z DTSTART: 20060104T140000Z DTEND: 20060105T220000Z Freebusy; FBTYPE = BUSY - TENTATIVE: 20060104T150000Z/PT1H Freebusy: 20060104T190000Z/PT1H END: VFREEBUSY END: VCALENDAR software


The list of CalDAV clients includes:

  • Atmail (version 6.0 )
  • CalendarSync for Android
  • CalDAV TaskSync for Android
  • CalDAV - Sync for Android
  • DAVdroid for Android (open source)
  • Evolution ( Linux, Unix, Windows)
  • Horde Groupware
  • ICal ( on Mac OS X Leopard - 10.5)
  • IPhone (version 3.0 or version 2.1 with Remote Calendar)
  • Microsoft Outlook with ZideOne plugin ( no longer available ), Open Outlook Connector ( asleep Development, advancement is SOGo ) Bynari WebDAV Collaborator or iCal4OL
  • Sunbird or Thunderbird with the Lightning add-on (Linux, Windows, Unix, Mac OS X)


The list of CalDAV Server includes:

  • Apple's Darwin Calendar Server
  • Atmail (version 6.0 )
  • Baïkal Lightweight CalDAV CardDAV server
  • Bedework (formerly UWCalendar )
  • Bynari Collaboration Suite
  • Chandler Server ( Cosmo )
  • CommuniGate Pro from version 5.2
  • DAViCal
  • DavMail
  • Daylite CalDAV server
  • Dingo Calendar Server
  • DPCalendar
  • EGroupware from version 1.6
  • EVO mail server
  • Folio Cloud
  • Google Calendar (incomplete implementation regarding invitations)
  • Horde Groupware
  • Icewarp e- mail server from version 8.x
  • IT Hit WebDAV Server Engine for. Net
  • Kerio Connect
  • Mod_caldav
  • Oracle Beehive
  • Oracle Communications Calendar Server
  • ownCloud
  • ( Project to be set translucent ) PHProjekt
  • Radicals ( CalDAV )
  • SabreDAV
  • SOGo
  • Scalix
  • Sun Java Calendar Server
  • Sync • gw
  • Synovel CollabSuite
  • Yahoo Calendar
  • Zarafa from version 6.30.0
  • Zimbra from version 4.5