@kathe , the Commonsense book is approachable. I’ve used Wikipedia a bit and material I find on Google scholar, but have yet to write my own event calculus code. I’d be happy to correspond with you here or privately if we both dive-in to this topic.
@jan thanks for the link to Mr Gupta’s page. Also, you aren’t just a regular Prolog programmer, you are “the” Prolog programmer everybody should aspire to be. 
I’m assuming you’ve seen this? GitHub - aartikis/RTEC: RTEC is an Event Calculus implementation optimised for stream reasoning
This looks vaguely familiar but I’m now looking at it with renewed interest thanks to your post!