定语从句 the day 后面什么时候接when 什么时候接on which

定语从句 the day 后面什么时候接when 什么时候接on which

一，具体看先行词前是否可以搭配这个介词. 
1，如 i will never forget the day when i met him. 
这个句子的when 可以用 on which 代替,因为我们平时的搭配就是 on the day. 2，但是如果句子是　I will never forget the year when i met him. 
这个句子的when 就不可以用on which 而要用　in which,　因为我们平时不说 on the year而说 in the year .
3，有时也会用到at /during+which 
如.That was the time when(= at which) he arrived, 
或者 it rained heavily when (during which) we stayed together.
二，on which也有可能是where的意思 
比如 this is the desk on which i found my pen这里的on which就不能用when.

when可以用 介词+which来代替，而on which只是一类情况，具体看先行词前是否可以搭配这个介词.
如：It was raining on the day when(on which) Peter arrived. 
i will never forget the year when（in which） i met him.
That was the time when(at which) he arrived,.