En vs Dans (Time)

While studying, I realised that there were different in, at  words used in French which got me confused. I did a little digging and am trying to understand how en is different from dans.

E.g. Je le ferai en trois jours vs Je le ferai dans trois jours.

Does en means I will do it within 3 days.

And Je le dans trois jours means I will start doing it 3 days later?

They both translate to I will do it in 3 days. However I understand they mean very differently.

That is a really interesting question, ChuaJ ! Especially since it's actually the English usage of just the one word that gives rise to the confusion. The use of two different prepositions in French sorts out the intended meaning very nicely.

And you are basically correct in your deductions:

En + time/duration expresses the time required.

Dans + time/duration expresses the time until.

There's a nice concise discussion in this article:

https://french.kwiziq.com/revision/grammar/talking-about-time-when-to-use-en-versus-dans-prepositions-of-time

Of course, there's more to say about choosing between these two prepositions that would be outside the scope of your question. But for the sake of completeness:

https://www.thoughtco.com/learn-essential-french-prepositions-4078684

and

https://www.mytutor.co.uk/answers/3316/IB/French/How-to-use-the-prepositions-en-and-dans-in-French/

Robert

Bonjour!

This is an interesting topic and RobertC106 has covered it pretty well, but I thought I'd build upon it. RobertC106 is completely right in saying:

En + time/duration expresses the time required.

Dans + time/duration expresses the time until.

There is another trick to distinguish when to use these two prepositions. Both prepositions can be used to express a point in time, however one is in the future and one is in the past.

Dans is used to express a point in time, however this is used in the future tense for an action that is anticipated to start in a certain amount of time.

     -     Je le ferai dans dix minutes. (I will do it in ten minutes.) 

i.e. the action will begin in 10 minutes time.

En is used to express a point in time and generally speaking that is expressed in the past tense. For example:

     -     Je l'ai fait en dix minutes. (I did it in ten minutes.)

i.e. the action was completed in 10 minutes.

We can do a direct comparison to see the difference. Imagine someone asks you to complete a task, you could say:

     -     Là, j'ai pas le temps, je le fais dans dix minutes. Mais c'est vite fait, je le fait en dix minutes.

     -     Right now, I don't have time, I'll do it in ten minutes. But it's quick, it'll take me ten minutes.

Note how the first sentence describes that the action will commence in the future (dans), while the second sentence describes how long it will take to complete the action.

I hope this helps,

   -   Mitchell