What is a word meaning "a non-instantaneous event"?
That is, an event which has some positive (possibly infinite) duration.
Solution 1:
Process is defined as a continuous action, operation, or series of changes taking place in a definite manner.
Another source defines it as a series of changes that happen naturally.
Solution 2:
Perhaps an "ongoing" event, or a "sustained" event?
"Continuous" event is another possibility.
Solution 3:
I would say that an event with a duration is an interval.