If you're worried about your digital privacy, you probably know that using Google apps is not ideal. Although the tech giant has taken steps to give people more choices about the data they share, it still has a lot of work to do. Fortunately, open source apps can help you keep your data secure, as none of your data within the app can be tracked or shared without your knowledge.

Google Calendar is an excellent calendar app. Still, there are plenty of open source alternatives available for Android. If you're willing to sacrifice some functionality, these apps should fulfill most of your calendar needs. If you've just picked up a new Android phone, install one immediately to keep your data secure.

Why open source apps matter

Free and open source software (FOSS) has several advantages, but to most people, the main benefit is privacy.You'll want to check out our in-depth open source explainer, if you're not familiar with the term, but here's the quick version: With open source apps, all the code is out in the open, so anyone with programming knowledge can go through it and see what an app is doing behind the scenes. Proprietary apps are black boxes where you don't know what's happening behind the scenes.

While nothing stops open source app developers from spying on people, the behavior is not common. Open source software and apps can also be audited their users and other developers, so any unsavory practices are likely to be caught quickly.

There are plenty of incredible Android open source apps in the Google Play Store, but we think downloading a solid calendar replacement is a good start. Here are our top picks for open source calendar apps you'll find on the Google Play Store.

Simple Calendar

Simple Mobile Tools offers a brilliant range of open source apps, and its calendar app is one of the best. The free version provides you with everything you need, including a search function, widgets, notifications for reminders, multi-calendar support, no advertisements, and more. If you want to use local calendars, you can quickly import and export .ics files.

While the free version of Simple Calendar has the core features you need, the Pro version has more notification and invitation options. We recommend upgrading if you use the app regularly.

Simple Calendar's interface is similar across all Simple apps, so this is an ideal solution if you want to use a unified suite of open source apps.

Etar

Another excellent open source option is Etar. It's lighter on features than Simple Calendar. Still, it has month, week, day, and agenda views, along with light and dark themes, notification support, no advertising, and a clean design. You can also import and export calendars in .ics format or import calendars directly from Google Calendar.

Proton Calendar

Proton Calendar is developed by Proton Technologies, which also developed a privacy-focused email app. Proton Calendar is developed with the same idea in mind, offering zero ads and trackers, end-to-end encryption, and no data sharing.

However, it lacks common features that are present in other calendar apps, like notes, and the ability to import .ics files. Still, it's perfect for those who aren't heavy users of calendar apps, as it includes the most important features like event notifications, a calendar widget, daily and monthly views, and recurring events. Upgrade to the paid version to manage up to 20 calendars.

DAVx⁵

DAVx⁵ isn't a calendar app on its own. Instead, it acts as a sync server for other calendar and contacts applications to access cloud accounts. If you switch devices regularly, this can sync your calendar without needing to use Google Play Services.

DAVx⁵ can pull data from most cloud services, including iCloud, Google, Nextcloud/OwnCloud, Fastmail, Synology DSM, Yahoo, and many others. Because it acts as a CalDAV provider for the Android system, most contacts and calendar apps should be able to access it, including the ones that ship with your phone.

There's no shortage of open source app alternatives

The limited range of open source calendar apps on Android can feel frustrating. However, many open source email apps include a calendar feature, so it's worth trying one of these out instead of a dedicated calendar app.