Best Open Source Android Calendar Apps For Privacy in 2022

If you’ve switched to a digital calendar, have you thought about how much your calendar events could reveal about you? Regular work events could reveal both where you work and the times when you are not home. An appointment with a therapist could reveal brewing marital problems. Parties could reveal to insurance companies that you are likely engaging in reckless behavior. I could go on.

Let’s learn how to protect this data and keep your personal schedule private. In this article I will cover the best calendar apps for Android that will help you to ditch privacy-invasive services like Google Calendar.

The best way to protect your calendar data is to keep it stored locally on your own device and not on any cloud service. The most feature-rich, privacy-respecting calendar app for Android at this time is called Etar. The app is available on both the Google Play Store as well as F-Droid.

In this post, I’ll cover the best, private calendar applications currently available on F-Droid and compare their features to the built-in Android Open Source Project (AOSP) calendar. Several of these apps will let you store and sync your data locally as opposed to cloud-based apps like Google Calendar or Microsoft Outlook. Having local control of the sensitive data about your events, meetings, vacations, etc., is much better for privacy than having to trust that one of these providers is keeping your data secure and not selling it to third parties.

F-droid is an alternative app library to the Google Play store for Android devices. The library consists of vetted, free and open-source software (FOSS) projects, many of which you can’t find on Google Play. For those seeking privacy-respecting software or setting up a de-Googled Android device, F-Droid is an essential resource.

I wrote a helpful guide all about F-Droid, so if you’re new to this app store check out that article here.

Feature Comparison Table

Feature	AOSP	Etar	Simple	Tutanota	Proton
Month View
Week View
Day View
Agenda View
Dark Theme
Export
Offline
CalDAV
EteSync
Widgets

The Default Calendar App (AOSP)

As you are probably aware, most Android phones come with a default calendar app already installed. The main problem with using this calendar is that it will be linked to the Google account used on your phone. Thus, by default, any events you add to this calendar are not actually stored on your phone, they are synced with your Google account.

Now, if you have a de-Googled phone and are not signed into a Google account on your Android device, then you don’t have to worry about syncing with Google. The problem for you is that each calendar has to be linked with an account for the default calendar app to work, so by default you won’t have any calendar account to add events to. Another issue is that, if you don’t have this app installed automatically (e.g. on Graphene OS), the app available on F-Droid hasn’t been updated since 2013.

There are apps on F-Droid that will allow you to add an offline calendar account and view it with the default (or any) calendar app, but I won’t go into these here because I think there are some better options. Let’s now take a look at the best open-source calendar apps out there for privacy-focused Android users.

1. Etar

Etar is an enhanced version of the built-in Android calendar. It is a fully-featured application that can handle complex repeating event schemes, syncing, as well as importing and exporting. It can sync with any email-based calendars like Google or Exchange as well as any other CalDAV server. It also has the capability to do EteSync, in addition to simply having offline, locally stored calendars. It features a dark and pure black theme, and includes a nice agenda view widget.

Personally, I use Etar over Simple Calendar Pro because I like the look and feel of the user interface better. They are both good options, though.

2. Simple Calendar Pro

Simple Calendar Pro is part of a collection of open-source apps called Simple Mobile Tools meant to replace the system applications that typically come pre-installed on your phone. The developer’s goal was to create a suite of apps that had minimal permissions, expanded functionality, with a customizable user interface.

The calendar application is fully featured and customizable, including dark and black themes. It can handle complex repeating event schemes, syncing with CalDAV, and importing and exporting via .ics files. Offline calendars are an option with this app if you’d rather that your private data be locally stored. It also includes several elegant, transparent widgets in month, day, and agenda views with customizable colors.

Unfortunately, the free version is no longer maintained by the developer as of November 2018. However, this is only if you get it from the Google Play Store. The full, updated pro version is available for free on F-Droid. If you use F-Droid to get around the payment to Google, please consider directly donating to the developer instead.

3. Tutanota

Tutanota is an email provider that offers end-to-end encrypted email, contacts, and calendar. This would be a nice solution for someone who desires a calendar that will easily sync across devices and integrate with email and contacts. With this app you can import and export .ical or .ics files, but there is no CalDAV syncing or offline calendars. The app features a month and agenda view as well as dark mode.

4. Proton Calendar (Beta)

Brought to you by the developers who made Protonmail and ProtonVPN, the Proton Calendar app is currently in development and a beta version of the app is available on the Google Play Store at the time of writing. I will update this review once the full version becomes available, however the beta version does look promising.

Protonmail and ProtonVPN are widely used and trusted in the privacy community, including by yours truly. If you’re already in the Proton ecosystem, this calendar app could be a good solution for you. However, like Tutanota, you won’t be able to view the calendar through any other apps since it doesn’t support CalDAV and you will have to trust your data to the Proton developers since there is no offline option.

If you have a de-Googled device and the Play Store is not an option for you, consider downloading the app through the Aurora Store (available on F-Droid). Alternatively, in the near future you may be able to download the app directly from Proton.

5. DAVx5

DAVx5 isn’t actually a calendar, but is a client that enables synchronization of CalDAV (for calendars) and CardDAV (for contacts) servers on Android. Use this app to easily manage any calendar accounts that support CalDAV, from Google to Nextcloud. Once your accounts are set up, you can view your events with a calendar application like Etar or Simple Calendar Pro.

This could be a perfect option for you if you already host your own Nextcloud server and you need to sync your calendar between devices. This software let’s you create your own personal cloud for file syncing, but has so many more features with the multitude of available add-ons. A popular add-on is the Calendar, which lets you host your own CalDAV server that is under your control.

Conclusion

In this post, we’ve covered the best private calendar options on Android to make sure that your digital calendar data is for your eyes only. With these methods, you can rest assured that no Big Tech giant or unregulated data broker is going to get a hold of your private schedule.

If you’d like to learn more about why I care so much about Google collecting all this data and tracking everyone, click here to check out my article explaining the top reasons to care about Google tracking.

Lastly, I wanted to mention one other elegant solution to protect your private calendar information. That is the old school method of keeping a pen-and-paper calendar. While it won’t sync between devices, this is by far the easiest and most accessible way to keep a private, locally controlled calendar.

Happy scheduling!