"When did or will the event happen?" — This sounds silly to me.
To make matters worse, I would like to use passive voice because the question is in reference to a statement that uses passive voice.
"When were or will they be punished?" — This is especially bad because it sounds like "When were they be punished?" is an optional way of receiving the question.
Any answer is appreciated, but I'd really like to do this using a single sentence.