"Le jour ________ j'arrête de fumer, les poules auront des dents."

Question

Eight years ago Meike asked about this and there was no good answer.  I’m confused about the same thing.  The lesson doesn’t discuss using ou when the clause contains the future tense.

Céline Pickard · Accepted Answer

Bonjour Julia,
I am sorry Mieke's question wasn't answered earlier.
In French, où works the same way no matter what tense follows it:

Le jour où j'arrête de fumer ... = The day I stop smoking ...
Le jour où j'ai arrêté de fumer ... = The day I stopped smoking ...
Le jour où j'arrêterai de fumer ... = The day I will stop smoking ...

Thanks to your comment, we have added an example to avoid this ambiguity.
I hope this is helpful.
Bonne journée !