build過去將來時表示什麼

不能説將來過去時，應該是過去將來時，其結構是 “would + 動詞原形”，指的是發生在過去某個時候以後的行為。

例如:

He said to me that his mother would come and see him soon. 過去將來時would come and see 發生在said 以後。

If I were you， I would not make friends with him. 要是我是你，我就不會和去他交朋友。虛擬語氣的過去將來時would not make在虛擬動詞 were 以後。