in加一段时间有两种含义.

in加一段时间与现在时,过去式连用表“'在某段时间内”,一般与完成某个动作有关.

I always eat my lunch in 15 minutes.

I finished my homework in 2 hours.

in加一段时间与将来时连用表示“.时间之后”.

My father will come back in 2 weeks.