Local calendar Protocol

I have entered a rabbits warren of attempting to setup a control panel for HA and also family planning. What I have found is there is no real solution for a local privacy centric solution to this that can replace say Google calendar.

There are a few options but all are fundamentally caldav and this means they integrate into HA OK but things like creating entries from HA becomes difficult

Not really a HA thing but I see this as something for Open Home Foundation that would work with HA.

Something that works with Android and iOS and HA / web can’t be that difficult to implement but would be better than caldav which is a horrible protocol.

This is entirely local:

Yes but pretty limited and is in no way a replacement for say Google calendar.

My thought here is that by having something better than iCal you can sync it to this (like I currently do with my Google calendar) but be able to interact with it outside of HA. IMHO HA is for automation so should use calendars like this not be the source of them.

This is why I see it as an Open Home Foundation thing rather than HA (but there isn’t a OHF forum).