While you may have already checked out our list free and open source Gmail alternatives, you may not even be aware free and open source alternatives to the likes of Google Calendar are out there.
If you want to keep your schedule private — or simply don't want anything to do with Google — there are some totally decent options available for Android that you should check out.
Many people simply prefer open-source apps out of principle, in the same way that some people prefer shopping at locally-owned stores instead of Walmart or Target.
When I asked social media for open-source alternatives to Google apps, the Simple Mobile Tools series of applications was brought up by many.
Primarily developed by Slovakian-based Tibor Kaputa, Simple Mobile Tools is a suite of productivity apps that mirrors the ecosystems you get from the likes of Google, Microsoft, and Apple.
Simple Calendar has pretty much everything I want out of a calendar app — a search function, widgets, notifications for reminders, multi-calendar support, no advertisements, and more.
The app also fully supports CalDAV, so it can sync calendars from any accounts set up on your phone — including Google Calendar, Outlook, NextCloud, and so on.
Like Simple Calendar, it can pull calendars from Android's built-in CalDAV service, so my Google Calendar schedules appeared with no effort
DAVx⁵ isn't a calendar app on its own — rather, it acts as a sync server for other calendar and contacts applications (including the ones mentioned above) to access cloud accounts
For example, you could use DAVx⁵ to sync your Google Calendar and Contacts to a device without Google Play Services
Because it acts as a CalDAV provider for the Android system, most contacts/calendar apps should be able to access it, including the ones that ship with your phone
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