Using preposition in

Noname 8048Is it even correct to say 'in' with period time describing past event ?

Yes. That sentence is correct and common.

The tower fell down in three months. (The tower fell down three months after it was built, or after it burned, .... )

Other similar sentences:
Let's leave in five minutes.
He will be back in an hour.

Thanks for replying.
But your sentence is describing future events and my sentence describes past event.
I'm still not sure if I can use 'in' to describe past events.
Followings are meaning of 'in' from Oxford Dictionary.

2. Expressing a period of time during which an event happens or a situation remains the case:
'Most people come to my farm in the afternoon and have trav

Noname 8048The tower fell down in three months.

It fell down after three months (point) OR It took three months for it to fall down (gradually crumbling) (period). It depends on context and, especially, the type of verb.

Similarly, both in the past:

(I planted the seedlings in March.) The seedlings grew an inch in two weeks. (period

I can understand the first example of yours.
And your second example.
Those that mean 'He resigned after six months'?
I never thought 'in' can be used like 'after' except for indicating future events.
These are what I have thought to describing a guy resigning after six months.
-He resigned after six months.
-He resigned in sixth month.
-He resigned working for six mont

Noname 8048Can I say something like this? : It was built in more than 100 years.

Not if you mean "after more than 100 years". No.

In fact, once you start adding things like "more than", using "in" doesn't work as well. However, you can say

It was the first one of its kind to be built in more than 100 years.
~ More than 100 years passed

So "It was built after more than 100 years" is correct sentence and a sentence of 'in' replacing after is wrong?
And that is because of usage of things like 'more than'?
Why 'in more than' is wrong when 'in' can be meaning 'after'?
I think these are all the question I need for completely understanding 'in'

Lastly, the example you gave me is very confusing :[
If you don't m

Noname 8048I'm still not sure if I can use 'in' to describe past events.

Yes, consider these past events:
Q- When did you get married and what year was you first child born in?
A- I got married in 1980 and Nick was born in 1982

Anonymous Noname 8048I'm still not sure if I can use 'in' to describe past events.Yes, consider these past events: Q- When did you get married and what year was you first child born in? A- I got married in 1980 and Nick was born in 1982

I mean period of time in the past.

Noname 8048 period of time in the past.

So 1982 is not a period of time (one year) in the past?

Time expressions with "in" are used in the present, the past, and the future. We have given you numerous examples.

I tilled the ground in March, planted the seeds in the first week in April, and they sprouted in two week

Oh, actually I was confusing if I can use 'in' like after the past event just like the example "He resigned in 6 months"
In the sentence 'in 1965' 1965 is period of time.
But in give example, 'in' can be used like 'after', and indicates the point when he resigns and No guides or dictionaries seem to calify second usage of 'in'
Did some searching and now I'm even confused of what