Best Calendar 366 Alternatives in 2026
Updated
20 apps from calendar apps ranked against Calendar 366 on the same published basis.
- 1Calendar 366 vs Mozilla Thunderbird
- 2Calendar 366 vs Microsoft Outlook Calendar
- 3Calendar 366 vs Lark
- 4Calendar 366 vs EGroupware
- 5Calendar 366 vs Proton Calendar
- 6Calendar 366 vs Teamup
- 7Calendar 366 vs Cozi
- 8Calendar 366 vs Calendar.com
- 9Calendar 366 vs TimeFinder
- 10Calendar 366 vs Notion Calendar
- 11Calendar 366 vs TimeTree
- 12Calendar 366 vs Fantastical
- 13Calendar 366 vs Doodle
- 14Calendar 366 vs Tuta Calendar
- 15Calendar 366 vs Reclaim AI
- 16Calendar 366 vs FlowSavvy
- 17Calendar 366 vs Musubi
- 18Calendar 366 vs Samsung Calendar
- 19Calendar 366 vs Trevor AI
- 20Calendar 366 vs Calendars by Readdle
Calendar 366 alternatives compared
| # | App | Score | Free plan | From | Runs on |
|---|---|---|---|---|---|
| 1 | Mozilla Thunderbird | 9.0 | Free plan | Free | Android, Linux, Mac, Windows |
| 2 | Microsoft Outlook Calendar | 8.2 | Free plan | $1.67/mo | Android, iOS, Mac, Web |
| 3 | Lark | 8.2 | Free plan | Android, API, iOS, Linux, Mac, Web, Windows | |
| 4 | EGroupware | 8.2 | €21.90/mo | Web, Linux, Windows, Mac | |
| 5 | Proton Calendar | 8.0 | Free plan | Free | Android, iOS |
| 6 | Teamup | 8.0 | Free plan | $12/mo | Android, API, iOS, Web |
| 7 | Cozi | 8.0 | Free plan | $3.25/mo | Android, iOS, Web |
| 8 | Calendar.com | 8.0 | Free plan | $20/mo | Android, API, Browser, iOS, Web |
| 9 | TimeFinder | 8.0 | Free plan | Free | Android, iOS, Mac, Web, Windows |
| 10 | Notion Calendar | 7.9 | Free plan | Free | Android, iOS |
| 11 | TimeTree | 7.9 | Free plan | $3.75/mo | Android, iOS, Web |
| 12 | Fantastical | 7.9 | Free plan | Free | iOS, Mac, Windows |
| 13 | Doodle | 7.8 | Free plan | $11/mo | Web |
| 14 | Tuta Calendar | 7.8 | Free plan | €3/mo | Android, iOS, Linux, Mac, Web, Windows |
| 15 | Reclaim AI | 7.8 | Free plan | $10/mo | Browser, Web |
| 16 | FlowSavvy | 7.8 | Free plan | Android, iOS, Web | |
| 17 | Musubi | 7.8 | Free plan | Free | Android, iOS, self-hosted, Web |
| 18 | Samsung Calendar | 7.7 | Free plan | Free | Android |
| 19 | Trevor AI | 7.7 | Free plan | $0.42/mo | Web |
| 20 | Calendars by Readdle | 7.7 | Free plan | $1.67/mo | iOS, Mac |
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Questions about Calendar 366 alternatives
What is the best alternative to Calendar 366?
Mozilla Thunderbird, number 1 in calendar apps with a score of 9.0 out of 10. The others here: Microsoft Outlook Calendar, Lark, EGroupware and 16 more.
What is the best free alternative to Calendar 366?
Mozilla Thunderbird is the best-ranked alternative with a free plan. 19 of the 20 alternatives here publish a free plan on their own pricing pages.
Is there an open-source alternative to Calendar 366?
Yes: Mozilla Thunderbird, EGroupware.
How are these alternatives ranked?
Ranked free-and-open first: a usable free tier and open-source code, then the platforms it runs on and its documentation.