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"People have made painstaking efforts to restock the nation's forests in the six decades that have passed since the end of the Korean War."

I have seen the sentence in a news article and I think that for the six decades are more natural or is there a reason in is used there and is there a meaning difference between in the six decades and for the six decades?

Thank you so much as usual in advance.
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Hans51"People have made painstaking efforts to restock the nation's forests in the six decades that have passed since the end of the Korean War."
In is better. It means "during."
Comments  
Students: Are you brave enough to let our tutors analyse your pronunciation?
Thank you and I have learned that during is used with events like during sunmer / a vacation and for is used with numbers like for two days / six months. What I know is wrong?
During can be used with almost any time period:

During the war years
During the six decades following the peace treaty
During the night
During his lifetime
During my school years
During the past two weeks
During the past three minutes

etc.
Use "during" when something happened between the beginning and end of the time period.

During his lifetime, he never drove a car.
During his lifetime, he visited Japan several times.
I received four hundred messages from him during the past twelve hours.

Use "for" when something happened (nearly) continuously between the beginning and end of the time period:

I studied music for three years.
He has had that car for six months.
He's sent me messages every two minutes for the past twelve hours. I received almost 400 messages from him in the past twelve hours.