when加过去式 的用法 比如 sb did sth等等

I didn't konw when he would leave.
I didn't konw where he would go.
I didn't konw what he would do. (would 是will的过去式）
看出了吗?when 和 后面的内容只有 逻辑上的关联.
when加过去式 的用法 比如 sb did sth：即是 when+句子,句子是过去式只是表明发生在过去的事情.
when+句子：是一个名词性结构,具有名词的作用,可以作主语,宾语,表语,同位语.
I didn't konw when he would leave.（作宾语从句）
where he would go was what she cared.（主语从句）
what she cared was where he would go （表语从句）

1 当.....时候（引导时间状语从句，从句中动词可以是瞬时，也可以是延续）
2 作突然讲，用于几个固定句型：be doing.......when be about to do when .......
had done ......when......
3 作...