在一般情况下，当主句为通常以后时的时候，时间状语从句和条件状语从句要用通常目前时，而不可以直接用通常以后时。如：
If you don’t go, I will not go either. 你若不去，我也不去。
When it gets warmer the snow will start to melt. 天气变暖时，雪开始融化。
但有时从句可以用目前完成时，能请老师讲讲这方面的使用方法吗？
目前完成时，用在时间状语从句或条件状语从句中，表示以后业已完成的动作或状况，代替以后完成时。比如：
Ill go to my grannys as soon as I have finished my homework. 我一完成作业就去奶奶家。
As soon as he has regained his memory, the problem will be solved. 只须他一恢复记忆，问题就能解决了。
once we have promised, we should keep it. 一旦许下诺言，大家务必遵守。
We cannot move him from any decision once he has made it. 他一旦做出决定，大家就没办法使他改变。
Put the book back when you have done with it. 你读完这本书时把它放回原处。
When you have formed a plan, you must carry it out. 计划订出之后，你需要贯彻实行。
The hen cackles when she has laid an egg. 母鸡下蛋就咯咯地叫。
If you have finished reading the book before I leave，please lend it to me. 假如你在我离开之前就读完了这本书，请借给我。
If he has written the letter, Ill post it. 假如他写完了信，我就把它寄走。
You can watch TV as long as you have finished your homework. 只须完成了作业，你就能看电视。
As long as you have passed the previous three relevant practice game, we can end the confrontation between rivals. 只须你通过了前面三关的训练赛，就能对决最后的对手。【注意】以上每个从句中，大家可以用通常目前年代替目前完成时，意思差别不大。
