六十前后花开日的意思:in 5 hours'time 中的in 是虾米意思？

in 5 hours'time 中的in 是虾米意思？ in time on time I______finish the homework in 2 hours. He will be back in two hours. AROUND THE WORLD IN EIGHT HOURS AROUND THE WORLD IN EIGHT HOURS in one's spare time=in one's free time? go back in time somewhere in time in time 是什么意思？