I want to add the release dates into my own/org calendar.
Does anyone know of a public ical or any other format we can use?
The help section of status.salesforce.com provides Swagger docs about public APIs.
Here is the link to documentation to retrieve maintenance infos: https://api.status.salesforce.com/v1/docs/#/maintenances/getMaintenances
You could call these APIs and retrieve the data into your org calendar.
(I have not tried calling these APIs, but it might be worth checking out)
AFAIK nothing publicly available. Just saw this idea, but still have few votes: https://ideas.salesforce.com/s/idea/a0B8W00000GdXDGUA3/publish-the-salesforce-release-calendar-as-an-ical-feed?sfdcIFrameOrigin=null