Tuta Calendar is part of the Tuta (formerly Tutanota) suite, a German secure email and calendar platform launched in 2014. All calendar data (events, reminders, contacts) is end-to-end encrypted, meaning only the user can decrypt it. The calendar is zero-knowledge (the company never accesses unencrypted data) and uses quantum-safe encryption. It integrates with Tuta’s encrypted email and offers web and mobile clients, all with strict privacy.