Compare software

Etar vs OneCalendar: catalog facts
Etar	OneCalendar
Free Free and open source.	Free Free to download from the app stores.
Android	Windows, macOS, Android, iOS
Open source with an active community Clean Material Design interface	Supports Google, Outlook, Exchange, iCloud, CalDAV and many other providers Available on Android, iPhone, iPad, Mac and Windows
Android only Sync depends on the calendar accounts set up on the phone	Closed source No Linux version
Downloadable app	Downloadable app
Open source	Closed source
License: GPL-3.0	License not stated
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.