定语从句说什么时候用when什么时候用which弄不清`

首先要读从句，看内容是否完整，

A.当缺主语或宾语时，用WHICH；
That was a fault which (could not be forgiven ).

I'll never forget the day _which__ we spent in Beijing.
We spent the day in Beijing.作宾语用which

B.当句子有主语谓语宾语，就可能是补状语了，用WHEN/where
1.I'll never forget the day _when_ (I first went to school).
I first went to school on that day. 做状语用when

2.This is office _where__ (Lincoln once worked ).
Lincoln once worked in this office

你记住 when = on which which = the day 基本上就不会混淆了。
比如。 i remember the day when we visited China.
因为这里的从句本来是 we visited China on the day.

时间用WHEN、IN WHICH，物用WHICH。

when = on which which = the day