I was confused here for the second paragraph why it was Un Jour, Robert ecrivait instead of a ecrirt. Isn't passe compose suppose to happen when specific events happen(Because of the "Un Jour") @StéphaneGimenez @LukeSawczak @LPH

It sets up a context

Yep, “quand tout à coup” introduces the event, while the first part of the sentence just sets up the context.

Yeah but when it says "Un Jour" Its referring to a specific date right?

So isnt ecrire gonna be passe compose?

The explosion happened while he was writting.

Imperfect vs passé composé (or passé simple in books) isn't easy.

The main uses of imperfect are describing things that were ongoing, that were true, or recurring. So it's actually a bit broader in scope than the past continuous tense in English. “Setting up a context” is, in my opinion, the right way to think about it.

@StéphaneGimenez Ah since "quand tout a coup" introduce the sudden event , it becomes avoir