in 2 months/ in 2 months' time.

[saloom2]

Which is more natural? And why?


My brother is going to stay with us in 2 months's time/ 2 months.

 

[MathiasPedersen]

2 months

When you use the "2 months's time" it is a genitive, but actually to make it a proper genitive it has to be "2 months' time"
If you do not know what I mean when I say genitive it is something belongs to the object e.g. "the boy's book" or in plural "the boys' books"

 

[5jj]

Both are equally natural. As Mathias said, the apostrophe needs to be after the s.