初四的定语从句that和 when的区别

I never forget the days ( )I spent with my nearest friend.
A that B when 答案给的A 可是我想知道B为什么不对，when不是也引导先行词为时间的定语从句吗？

when引导的定语从句要求从句是一个完整的句子

比如：(1) I still remember the day when I first came to the school.
(2) The time when we got together finally came.
I first came to the school 和 we got together 都是完整的句子

而这里，I spent with my nearest friend. spend 缺少宾语 所以用that

在这类问题里，关系代词that一般在定语从句中做宾语，关系副词when在定语从句中作状语。所以做这类题只要看一下后面的定语从句是缺宾语还是缺状语就知道是该填that还是该填when了。
I spent with my nearest friend. 句中spent缺宾语，所以填that，选A。
再举一个填when的例子：
I will never forget the days ( ) I lived with my grandma.
I lived with my gramma. 谓语live为不及物动词，后加介词短语作状语，和奶奶生活在一起，这里显然不缺宾语，而是缺一个时间状语，所以这里该填when.

分析定语从句的关键在于分析从句的句子成份。
看到时间，地点，原因不一定跟when, why, where。要首先分析从句的句子成分。从句中缺主语或宾语用关系代词。
关系代词：who, whom, which, that,
关系副词：when, where, why

从句中不缺主语或宾语才考虑用关系副词。spend 后缺宾语，所以用that
（1）This is the factory _______ I worked last year.where
(2) This is the factory ________ I visited last year.that

额，我都不知道该怎么用语法专有名词来解释了。。。。。。太久远了。。。