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Generally, the Open Web Calendar is there to be used without restriction. You can use this API to customize the calendar on the fly.

This section can be of use if one of these applies:

  • You are a web developer who wants to embed the Open Web Calendar.
  • You want to exploit the full flexibility, not just what is exposed on the configuration page.
  • You want to use JavaScript to dynamically generate the calendar design and options.
  • You want to extend the functionality of the Open Web Calendar.
  • You want to use the Open Web Calendar as a proxy to request JSON events for your self-made event feed.


The basic parameters are the same at these endpoints:

  • /index.html - edit the calendar
  • /about.html - view the about page
  • /calendar.html - view the calendar
  • /calendar.spec - download the specification
  • /calendar.ics - subscribe to the ics file
  • / - FLEXIBLE - get the events as JSON
    Please note that you CAN use this but you cannot be sure that the JSON schema remains the same. If you want that, add tests.

Additional parameters are required for /

  • timezone=UTC - the timezone that you need to display the events in
  • from=YYYY-MM-DD - the start of the period in which events happen (inclusive)
  • to=YYYY-MM-DD - the end of the period in which events happen (exclusive)


All configuration parameters are described sufficiently in the default_specification. That is the reference. E.g. if you find the parameter title in the default_specification, you have several options:

Change the title in a query parameter:


Change the title in a YAML specification:

title: calendar

Change the title in a JSON specification:

  "title": "calendar"

Adding Parameters

If you add a new parameter as a developer,

Compiling the Specification

You can change the calendar behavior and looks with parameters. These are the places to specify parameters:

  1. Query parameters
    All parameters to the calendar url are put into the specification. The query parameters have the highest precedence.

  2. specification_url
    If you specify this query parameter, the editor configuration is loaded from this url, too. Query parameters are still more important than what is written in this file. The source format can be YAML or JSON. Examples:

  3. default_specification
    This file contains the default parameters. They must not be hard-coded in the source code. All of them are there. Query parameters and the specification_url override these values.

Specification in the Calendar compiles the specification from the given parameters in get_specification(). In the template you can access the specification through the specification variable. The specification is available to JavaScript as the specification variable.

Specification in the Index Page

The default specification is available before the calendar is built via JavaScript in the configuration.default_specification variable. There is a getSpecification() function which created the specification from the inputs. Generally, the specification variable should be used.


Below, you can find a picture of the architecture.


The base of a calendar is the specification, given in the various forms. This specification influences all the steps.

After the specification is compiled, the calendar (ics) files are downloaded from the locations on the Internet.

From the calendar files, the events are generated.

Then, different views are chosen to display the events.

In the end, these lead to HTML and style changes of the calendar website.

In the real application, these steps are bit bit mixed up and unordered or omitted but this explains simply the basic, initial idea behind the event processing.