Difference between 'en' and 'dans'

I wanted to know if someone could clarify the difference between 'en' and 'dans'. Both words translate as 'in' From my understanding the word 'dans' is used when talking about something physically being in something. Ex. C'est dans le tiroir. (It's in the drawer) I have a good understanding of when to use 'dans' but I get confused when should I use 'en'. Can anyone help? please.

Both "dans" and "en" can be used to express time and location, however "en" is used to express the lenght of time something takes, as in " I learned how to speak French in eight weeks" whereas "dans" is used to express an amount of time before something happens. As in "I'm going to Paris in 2 weeks"