BookTime vs Tuta Calendar

BookTime has no write-up on Specifiction yet; its figures are above.

Tuta Calendar organizes appointments, business meetings, and repeating tasks across Android, iOS, Linux, macOS, web, and Windows. It supports shared calendars with read-only, read-and-write, or write-and-manage-sharing access. Calendar events, invitations, sharing, and push reminders are described as end-to-end encrypted. Users can send and receive invitations, including password-protected encrypted invitations to external users. Imported calendars sync automatically across devices, while the listed calendar sync type is one-way. Tuta says reminders are hidden from the phone operating system and can arrive offline. The calendar is integrated with Tuta email and contacts. Security features include two-factor authentication; Tuta also describes its clients as open source and its calendar as using zero-knowledge architecture. The Free plan includes one calendar. Revolutionary costs €3 a month, billed monthly, and Legend costs €8 a month, billed monthly; both include unlimited calendars. Tuta is made by Tutao GmbH, based in Hannover, Germany, and founded in 2011.