my calendar events were erased today

OSX9.5

I looked in my calendar, quit it, closed the lid on the MPB, took a train ride, opened the lid, opened calendar and all events in past and future were gone.

NOT the groups.
NOT subscriptions to Facebook birthdays or special days or my personally entered yearly events.

"JUST" Every Event Ever marked with dates, and places and people and links and links and links and oh, how I hate digital media right now.

I have a month old back-up, which may give me back my past (if not the immediate future), I don't know. It's not a Time Machine (don't like the concept or the cloud, long story) - so, where are the relevant data stored, please?

Thank you.