我解答上述有关since的问题，目的是要告诉网友，since 后接的时间不是前面句子中的年份，而是谓语动作发生的时间。since when 来自于并列句中的，and since then, then=that time = 谓语动作发生的时间。如果谓语动词是died, then就是指死亡的那一天、那一刻，而不是指那一年。逻辑是，自从他与某年死后，而不是自从某年。这就是为什么since后不能用which引导定语从句。

during则不同。during是补充说明这一年的，所以你可以用during which。

He sat on the roof of the house, and from there/from that place he could see the mountains in the distance.

上述并列句中from介词短语的意思为，from the place where he sat  .这个并列句如果改为非限制性定语从句，只需删去并列连词，把指示副词there改为关系副词there，或者把指示限定词that改为关系限定词即可。

He sat on the roof of the house, from where he could see the nountains in the distance.

He sat on the roof of the house, from which place he could see the nountains in the distance.

本句不可以用from which 引导定语从句。