The Living Thing / Notebooks :

Calendars and contact databases, digital, use thereof

Google calendar, iCloud etc exist. I don’t use them. Gifting your entire personal schedule and confidential contact data to third parties of dubious motivation demonstrates a touching sense of the general benevolence of the world toward you in particular. However, sadly, this rainbows-n-unicorns worldview entails a disregard for the personal privacy and beliefs of those of your contacts who are not convinced that the apparatus of state and capital is at their personal disposal.

Jargon to know here: CalDAV and CardDAV are the de facto standards to sync your calendar and contact information, respectively. All you need is a server which talks those standards and you can use whatever client you’d like.

So! Running your own.