Question

引导定语从句修饰“day" 的关系副词"when"可省略吗

Answer 1

　　定语从句中只可作为关系代词”that/which“在定语从句中作宾语时可省略。关系副词”when、where“等不可省略。

　　例：

1. I have a mobile phone my father bought for me yesterday.

2. Yesterday I went to the library where there were many students.

Answer 2

当先行词是明确表示时间的时候，关系副词when是可以省略的，不过不常见而已。如：
The
day
they
set
out
was
cold
and
windy.