过去将来时表示从过去某个时间看来将要发生的动作或存在的状态，常用于宾语从句或间接引语中。过去将来时常用“would + 动词原形”或“was / were going to + 动词原形”来表达。
I didn’t know when he would go to the park.
He said that he would wait for me at the school gate.
用“was / were going to + 动词原形”，“was / were about to + 动词原形”表示将来的动作或状态。
She told me she was going to fly to Yunnan.
I was about to leave the house when the telephone rang.
He said the train was leaving at five the next morning.
He said he was coming to see me.