How to refer to the most recent incident happening before or at a given time?

I am tracking the times of occurrence for a certain type of event (e.g., car accidents). For a given time n, I want to refer to the most recent event which occurred at a time no later than n.

Is it correct to refer to this event as "the last event prior to and including time n"?

Would it be better to say "the last event to occur prior to and including time n" or "the last event to occur prior to or at time n"?