CMS-Buttler

CMSB Kalender is a lightweight availability calendar for WordPress. It reads events from one Google Calendar iCal URL and displays the current month as available or booked.
Included in this WordPress.org version:
<ul>
<li>Shortcode <code>[cmsbkalender]</code></li>
<li>One Google iCal calendar</li>
<li>Current month display</li>
<li>Free/booked color display</li>
<li>Mobile layout</li>
<li>Optional legend</li>
<li>Custom labels for available and booked days</li>
<li>Server-side iCal loading with configurable cache time</li>
</ul>
Larger CMS-Buttler calendar versions with extended functionality are available as separate products outside this WordPress.org plugin package: https://cms-buttler.de/cmsb-kalender/
<h3>More powerful CMS-Buttler calendar versions</h3>
The WordPress.org version is intentionally focused on a clear and lightweight free/booked month view. It is suitable when you only need to publish basic availability from one Google Calendar.
The larger CMS-Buttler calendar products are separate packages outside this WordPress.org plugin and are designed for halls, clubs, venues, municipalities, rental locations, sports facilities, and organizations that need more control over public availability.
Compared with many simple calendar plugins, the larger CMS-Buttler calendar versions focus on privacy-conscious occupancy display instead of publishing every event detail. They can show that a day is booked while hiding names, internal notes, rental details, or private information.
Additional capabilities available in the larger CMS-Buttler calendar products may include:
<ul>
<li>Multiple months instead of only the current month</li>
<li>Half-day and partial-day occupancy with diagonal day display</li>
<li>Configurable split hour for morning and afternoon bookings</li>
<li>Mouseover details for events that are allowed to be public</li>
<li>Privacy rules for private, confidential, and default-visibility Google Calendar events</li>
<li>Keyword-based hiding for event titles and descriptions</li>
<li>Description trimming from an internal marker such as <code>Intern:</code></li>
<li>Optional booked label when hidden event details are suppressed</li>
<li>Extended design controls for colors, borders, legend, navigation, and day shape</li>
<li>Manual synchronization for testing calendar changes immediately</li>
<li>Sync status with information about loaded, skipped, changed, and recurring events</li>
<li>Recurring Google Calendar event handling</li>
<li>Website-side calendar cache clearing without changing the Google Calendar itself</li>
<li>Larger package options for agencies or operators managing more complex calendar setups</li>
</ul>
These larger versions are especially useful when the public website should answer the visitor’s main question quickly: “Is this date available or already booked?” At the same time, internal information can remain inside Google Calendar.
More information is available at https://cms-buttler.de/cmsb-kalender/
<h3>External Services</h3>
This plugin can use Google Calendar / Google iCal when a calendar URL is configured by the site administrator.
Google Calendar / Google iCal: 
The plugin requests the iCal URL entered by the site administrator in order to load calendar events. The request is made server-side from the WordPress installation to the configured iCal URL. Data processed by Google depends on the calendar configuration and Google’s policies. 
Service provider: Google LLC 
Terms: https://policies.google.com/terms 
Privacy: https://policies.google.com/privacy

CMSB Kalender

Display Google Calendar availability as a simple free/busy calendar with a WordPress shortcode.

TruthMedia

Allows complex calendar management

CMSB Kalender vs WordPress Event Calendar