Calendaring Extensions to WebDAV, or CalDAV, is an Internet standard allowing a client to access scheduling information on a remote server. It extends WebDAV (HTTP-based protocol for data manipulation) specification and uses iCalendar format for the data. The access protocol is defined by RFC 4791. It allows multiple client access to the same information thus allowing cooperative planning and information sharing. Many server and client applications support the protocol. Extensions to CalDAV for automated scheduling are also standardized, as RFC 6638.
The CalDAV specification was first published in 2003 as an Internet Draft submitted to the Internet Engineering Task Force (IETF) by Lisa Dusseault. In March 2007, the CalDAV specification was finished and published by the IETF as RFC 4791, authored by Cyrus Daboo (Apple), Bernard Desruissaux (Oracle), and Lisa Dusseault (CommerceNet). CalDAV is designed for implementation by any collaborative software, client or server, that needs to maintain, access or share collections of events. It is developed as an open standard to foster interoperability between software from different implementers.[clarification needed]
The architecture of CalDAV (partially inherited from the underlying specifications) organizes the data (events, tasks, free-busy info, notes) in directories (collections), where multiple items (resources) reside. The resources and collections can be accessed by one or more users, using standard HTTP and DAV semantics to detect conflicting changes, or to provide locking.
For access control the concept of ACLs are used, so each operation (view, edit, delete etc.) can be denied or granted per user. Therefore the specification requires that CalDAV servers must support "WebDAV Access Control Protocol" (RFC 3744). The calendar resources must use iCalendar format, which allows the server to understand and process the data. Parsing the iCalendar items is necessary, because the server has to support a number of calendaring-specific operations such as doing free-busy time reports and expansion of recurring events. With this functionality, a user may synchronize his or her own calendar to a CalDAV server, and share it among multiple devices or with other users. The protocol also supports non-personal calendars, such as calendars for sites or organizations.
Oracle Beehive, a unified communication and collaboration software solution, supports a number of open standards including CalDAV. This allows Beehive to work with a number of calendaring clients including Apple iCal, Mozilla Lightning, and Mozilla Sunbird.
SabreDAV, a WebDAV framework for PHP, supports CalDAV since version 1.2.
SOGo, SOGo is fully supported and trusted groupware server with a focus on scalability and open standards.
Synchronica, a developer of mobile push email and synchronization solutions announced that their Synchronica Mobile Gateway and Synchronica Mobile Backup products are both fully compatible with the CalDAV standard, allowing compatibility across a wide range of calendar applications.