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
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,
All you need is a server which talks those standards and
you can use whatever client you’d like.