Just a guess, but to auto-populate a calendar with country specific national and regional holidays would require either using (storing) a user’s IP geolocation or asking the user to reveal their country location. Either of which, I feel, goes against Tuta’s privacy philosophy.

There’s also a chance that a good chunk of Tuta users are behind a VPN lol, so IP geolocation is no bueno.

We can also download and import holiday calendars into Tuta: https://www.calendarlabs.com/ical-calendar/