I plan on adding ICS export and DM reminders. Those are manual now but will have automated soon.
Not what you asked for but nostr:npub18ams6ewn5aj2n3wt2qawzglx9mr4nzksxhvrdc4gzrecw7n5tvjqctp424 takes Nostr calendar events fully Nostr native.
Discussion
ics export would be a static file per event? would be cool as a subscription per npub or npub + hashtag so plebs can just see new events hit their calendar automatically