It is not necessary to have every feature I mentioned in the question title.
The point is most probably a nice modern open source calendar application, but the real point is trying to have a complete overview not of one specific project but your entire life in general - how's your financial situation, what upcoming dates are there, even saving critical documents in one place like tickets, registration documents, medical documents, legal documents, etc.
Ideally it would be sort of a combination of a calendar, to-do list, and financial planning app, but at minimum, just a feature-ful open source calendar.
Thank you.