CalDavZAP is an open source CalDAV web client implementation released under GNU
Affero General Public License (version 3.0).

Main features:

* 100% JavaScript+jQuery CalDAV web client/application - no special server
  software required for standard setup (except the CalDAV server of course)
* server-based XML configuration generator (for special setup) with HTTP and
  LDAP authentication plugins
* asynchronous read-only and read/write calendar collection detection
* asynchronous background synchronization
* support for delegated calendars
* support for subscribed calendars
* time-range filtering (server support required)
* support for RFC compliant vCalendars (version 2.0) and automatic correction
  of most common errors in invalid vCalendars
* support for background calendars - if there is at least one event defined for
  the given day in a background calendar, the background color for that day
  will be pink/light-red

and much more ...

WWW: https://www.inf-it.com/open-source/clients/caldavzap/