Longman詞典在有關in作介詞時有壹條是這樣解釋的:
6. at the end of a period of time:(壹段時間的末尾)
I'll be with you in a minute.(壹分鐘過後,而不是壹分鐘之內)
The results will be announced in two weeks' time.(同理,兩周後宣布結果)
以上希望對妳有幫助。