Have you started using the new features in your Tuta Calendar
(and have you looked at the sneak peek of what's coming next 
)
https://tuta.com/blog/tuta-mail-calendar-updates-march
Now your encrypted calendar has:
Three-day view Calendar name in event preview Improved calendar repeat rules
@Tutanota Thanks for the update! Tuta Calendar works quite well for me, the main thing I hope could be added is being able to easily add public holidays (Country specific). Maybe there is already some solution for that?
@jjj You can subscribe to external calendars - like public holidays - with the paid version.
