过去将来时的五种表达形式
一、was/were going to + 动词原形
He said that he was going to live in the country when he retired.
他说他退休后要住在农村。
二、was/were + 动词-ing形式
Nobody knew whether the guests were coming.
没人知道客人们是否要来。
三、was/were + 动词不定式.
It was reported that another bridge was to be built across the Yangtse River.
  据报道长江上将要再建一座大桥。
注意："was/were going to + 动词原形"或"was/were +动词不定式完成式"可表示未能实现的过去将来时间的动作。
Last Sunday we were going to visit the Great Wall, but it rained.
上星期天我们本想去游览长城的，但却下雨了。（没有去成）
I was to have helped with the performance, but I got flu the day before.
我是打算帮忙演出的，但前天我感冒了。（没有帮上忙）
四、was/were about to do
"was/were about to do"表示说话的瞬间就会发生的动作。
I felt something terrible was about to happen.
　我觉得有可怕的事要发生了。
五、was/were on the point of doing
I'm glad you have come. I was on the point of calling you, but you've saved me the trouble now.很高兴你来了。我正准备给你打电话，现在你省去我这个麻烦了。
提示："be about to do" 和 "be on the point of doing"结构一般不与表示将来的时间状语连用，但后面可以接when引导的分句。
I was about to start when it suddenly began to rain. 我正要动身天突然下雨了
六、特定场合的一般过去时可表示过去将来时
  条件状语从句和时间状语从句中须用一般过去时代替过去将来时。
  例1：I didn't know when she would come, but when she came I would let you know.
　例2：I didn't know if she would come, but if she came I would let you know.
 
3) 在含有be about to do的句子中，不能再加时间状语。如：
Wrong: The medical team is about to start immediately.
Right: The medical team is about to start. 医疗队就要出发了。
七）be to do:
(1)表示事先商定、安排或准备要做的事情。如：
The students are to meet at the school gate tomorrow.
2）表示可能性，必要、责任、义务、禁止等。如：
Her necklace was not to(couldn't)be found. 她的项链不到了。
2) be going to do:
1) 表示将要发生的事情或打算最近要进行的动作。如：
It is going to rain soon. 快要下雨了。
2) 在含有条件状语从句的主从复合句中，主句一般不用be going to，而常用will（第一人称用shall）。如：
The football match will be put off if it rains tomorrow.
3) be about to do: reported
1) 表示即将发生的动作，在时间上指最近的将来。如：
We are about to start. 我们就要出发了。
2) 在含有be about to do的句子中，不能再加时间状语。如：
Wrong: The medical team is about to start immediately.
Right: The medical team is about to start. 医疗队就要出发了。