Compare software

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

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