Difference between "à quelle heure" and "quand"?

Question

It is unclear to me exactly what the distinction is between these two for asking questions beginning with when. Is there a well-defined difference?

For example, what is the difference here?

Quand est-ce que tu pars ?

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À quelle heure est-ce que tu pars ?

When should the one be used rather than the other, or does it vary based on context?

It was mentioned in an answer to a separate question earlier today that quand is more for asking about the date than the hour. Is that always true? Should quand never be used for asking about the time, in any context?

Answer 1

I think that "quand" is used in a much broader sense. So if you are asked:

Man: Alors, quand est-ce qu'on part ? {So, when / how soon do we leave?}

The answer will vary greatly:

Woman: Maintenant. {right now}

Woman: Seulement après avoir fait les devoirs. {after doing the homework}

Woman: C'est pour le mois prochain. {sometime in the next month}

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Whereas "à quelle heure" is focussed on a specific time period:

Man: Alors, à quelle heure est-ce qu'on part ?

Woman: Entre 12h et 15h.