定语从句Winter is the time of year______the days are short and n

绝对不会是that
应该是when
这是先行词为time 的定语从句,从句中主语是days,are short 形成系表结构,说明不缺主语,宾语,是主系表结构完整,缺状语,用关系副词,when

when，因为”冬季“是一个时间概念。

winter is (that) the days are short and nights are long
the time of year 可以认为是……的可以更详细一点吗？可以看成把 the time of year去掉，或者把of year去掉，或者去掉后面
1 winter is that/which the days are short and nights are ...