dans ou en

Question

In the test, it says -Il termine dans 2 minutes. shouldnt it be ..en 2 minutes. i have learnt that when some action finishes within a particular time we use en.

Accepted Answer

Radhika, 
Regardless of whether talking about an action starting or finishing, the choice between ' dans ' and ' en ' depends on whether you are 
describing/emphasising the point in time at which 'it' will happen (dans), 
or 
the period of time necessary/during which 'it' will happen (en). 
Just as in English, there is a difference in emphasis between using ' in ' or ' within ', as discussed in the lesson attached. It is not necessarily exclusively one word or the other, but the choice of word changes the meaning. 
 https://progress.lawlessfrench.com/revision/grammar/talking-about-time-when-to-use-en-versus-dans-prepositions-of-time

Answer

Just to provide a few examples to Maarten's explanation:
Il est 11h58, tu dois terminer dans 2 minutes. -- It's 11:58, you have to finish in 2 minutes.
In this example, the emphasis is on fact that something has to be finished by noon. The observation that there are 2 minutes left is secondary.
Tu dois terminer en 2 minutes. -- You have to finish in (within) 2 minutes.
Here, it is secondary what time you have to be finished by. All that counts is that you have 2 minutes to do it.
In everyday usage, the examples will not always be as clear-cut as the ones above. But the emphasis on either the ending (dans) or the period (en) is what determines which one to use.

Answer

Thanks Chris and Maarten