French phrase
Combien de temps à l'avance faut-il ~ ?
Meaning
How far in advance should you ___?
When to use it
Asks how far ahead an action should be taken. It is a polite way to ask about timing for plans or events.
Example dialogue
On devrait acheter les billets bientôt.
We should buy the tickets soon.
Combien de temps à l'avance faut-il acheter les billets ?
How far in advance should we buy the tickets?