Had I known about this computer program,a huge amount of time and energy （would have been saved）

题目

Had I known about this computer program,a huge amount of time and energy （would have been saved）
为什么不是 would have saved 有什么区别吗 能否详细讲讲

答案

时间当然是被节省,这是个对过去的虚拟,翻译,如果我们早些知道这个电脑程序,很多时间就会被节省