The Nostr calendar will be available on NostrNet with notifications and alarms, but not exclusive, it will also be available as a standalone app. 

It's not ready yet, but you can give it a try. Please let me know if it's working properly on mobile devices.

https://cal.nostrnet.work/ nostr:note1ct0pza3vfelnwn8dmywrnfsjv4jury0r94m7rrltkzznj5shcyuqhhmwxm