所谓错综时间
虚拟条件句即条件从句与主句所指时间不一致，如从句指过去，而主句即指的是现在或将来，此时应根据具体的语境情况，结合上面提到的三种基本类型对时态作相应的调整：
简介
If it had rained last night, the ground would be wet now. 要是昨晚下过雨的话，现在地面就会是湿的。
You would be much better now if you had taken my advice. 假若你当时听我的话，你现在就会好多了。
特别说明
条件从句用if I were…时，既可指现在也可指过去：
If I were you, I would stay. 我要是你我就会留下。
If I were you, I’d go to night school. 我要是你，我会上夜校。
If I were not busy, I would have come. 假若我不忙，我早就来了。
也可用if I had been you也表示过去：
If I had been you，I’d have taken the job. 我要是你，我就接受那份工作了。
通常情况下，在
非真实条件句中
主句和
从句的
谓语动词所指时间是一致的，但有时也可能指不同的时间，这时要根据上下文的意思采用不同的谓语动词形式
即：（有时if从句和主句所表示的假想情况时间不一致，如从句与现在
事实相反，而主句表示与过去事实相反,那么句子两部分的动词形式应作相应的调整。）
e.g If I had asked her for advice yesterday, I should know what to do now.
You would be much better now if you had taken the doctor’s advice.
If my parents hadn’t forced me to come , I shouldn’t be here now.
If the weather had been more favorable, the crop would be growing still better.
假设语气的两个子句之间，时间有可能不同、必须分别判断。例如：
If I had studied harder in school, I could qualify for the job now.
我在学校时要是有好好念书，现在就可以符合这项工作的要求了。
条件子句是过去时间（在学校时）的假设语气，要退后成过去完成式(had studied)来表示非事实。可是主要子句是现在时间(now)，只要用过去拼法的could
就可以表达非事实了，不需用到「过去+完成 (could have qualified)」。