How do I translate "the time when..." into French?

The simple answer to your question is: le temps oùAlthough English uses 'when' in constructions like these, quand cannot be used in FrenchIt's the moment when the train restarts DOES NOT TRANSLATE TO C'est le moment quand la locamotive se remet en marcheInstead, French uses the word où or the word queoù is used when the time you want to refer to is definite. In this case the time usually has a definite article.e.g le jour où je sortais = the day when I was going out que is used when the time you want to refer to is indefinite. In this case, as you would expect, the time has an indefinite article.e.g un jour que je sortais = one day when I was going out