Etar on nostr:npub1vyw6twg3kwef27wdffsxawmvcycy407cehx3kj8xn0v0v5nwrgps6plpqe is great especially if you want to sync with nostr:npub1d68csfa6zedqy8snkapyavfgsfv07szsj304w5h3eerh7k3v7y6q36zk0p

For e2ee encrypted calendar, EteSync has a calendar app.