En vs Dans

Question

I think the British and American English are a bit different, so I'm still not quite clear on this.

So does "Nous avons mangé en 40 minutes" means we ate for 40 minutes? The duration of our meal was 40 minutes? It took us 40 minutes to eat?

And "Nous mangerons dans une heure" means we will have to wait for another hour before we can eat, right?

Accepted Answer

I think it's the same in US and UK English:

Nous avons mangé en 40 minutes = "Over the course of 40 minutes, we ate." All of the sentences you wrote mean the same thing as this.

Nous mangerons dans une heure = yes, we will eat in an hour from now.

Answer

Why do we say "En quelle année" and not "an" despite the fact that we use "année" when we want to emphasize the duration?

Answer

Hi Emre Can,
We say 'en quelle année' for the sake of  euphony as 'quel an' sounds strange in French.
There are a few exceptions to every rule and this is one of them.
Hope this helps!