little did he know that the course of his life was about to change then 中为什么用did?

问题描述:

little did he know that the course of his life was about to change then 中为什么用did?
这句话的意思是他不知道他的生活的过程要变化。就解释一下为什么过去时就行了

因为后面有then 啊= =.then 是那时候的意思