By running my newsletters through local AI I could get a decent event calendar for myself. By collaborating when checking the result I can get around some of the shortcomings with AI.
Project: http://nowsletter.org/
Self host: https://github.com/joelgalvez/nowsletter
I like thinking of newsletters as a potential source of data. Not entirely public, not private either. Suitable for some local context, perhaps. Newsletters are also generally nice: Low tech, easy, distributed, basic sense of the audience, etc.