The most common and most likely answer to this crossword clue is the 7 letter word TIMINGS
I've seen this crossword clue in The Guardian
T
I
M
I
N
G
S
Buddy explains!

The straight part
We know that "when events happening" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case when events happening = timings.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TIMINGS mean?
TIMINGS noun- An occurrence or event.
- The regulation of the pace of e.g. an athletic race, the speed of an engine, the delivery of a joke, or the occurrence of a series of events.
- The time when something happens.
- The synchronization of the firing of the spark plugs in an internal combustion engine.
- An instance of recording the time of something.