Add Calendar section with privacy-respecting alternatives

README.md

@@ -36,6 +36,7 @@
 - [Bookmarking](#bookmarking)
     - [Book and web annotations](#book-and-web-annotationshighlights-management)
 - [Captchas](#captchas)
+- [Calendar](#calendar)
 - [Commenting Engines (disqus)](#commenting-engines)
 - [Cloaking](#cloaking)
 - [Cloud Storage](#cloud-storage)
@@ -317,6 +318,22 @@ Google captchas use cookies to track users and rank their IPs.
 
 [Back to top 🔝](#contents)
 
+## Calendar
+
+⛔ **Avoid**
+
+- **Google Calendar** - Tracks your events, integrates with Google's advertising ecosystem, and your data is stored on Google's servers without end-to-end encryption.
+
+✅  **Instead use**
+
+- [🤖](#icons) [Etar](https://github.com/Etar-Group/Etar-Calendar) - Open-source calendar app for Android that works with any CalDAV server.
+- [🤖](#icons) [Fossify Calendar](https://github.com/FossifyOrg/Calendar) - Simple offline calendar app for Android with widget support.
+- [🤖](#icons) [KashCal](https://github.com/KashCal/KashCal) - Offline-first Android calendar with iCloud/CalDAV sync, full-text search, recurring events, and home screen widget. Apache 2.0 licensed.
+- [Nextcloud Calendar](https://apps.nextcloud.com/apps/calendar) - Calendar app for Nextcloud with CalDAV support. Self-hostable.
+- [Proton Calendar](https://proton.me/calendar) - End-to-end encrypted calendar from Proton. Part of the Proton privacy ecosystem.
+
+[Back to top 🔝](#contents)
+
 ## Commenting Engines
 
 ⛔ **Avoid**