本句结构是：The time was a period
所以,这里the time就是the period of time的意思,因此,后面的引导词用when时,可用：during the time替代,也就是during which]
而且,先行词是一段时间（不一定是time),又可以说during +一段时间时,就可能用during which作为引导词如：
Do you still remember the weeks during which we stayed together?
We are to study in this university for fouryears,during which we shall prepare ourselves well for the society.
我们将在大学学习四年,在此期间,我们要为进入社会做好准备.
而during which time,往往可以换成：during that time指先行词的.
如
The interview lasted less than a minute,during which time I was sacked,not lauded.
但是谈话不到一分钟就结束了.我并未受到嘉奖,相反我被开除了.
这里就是：
The interview lasted less than a minute,and during that time I was sacked,not lauded.
再问： 四年和一分钟不都是具体的时间吗 为什么We are to study in this university for fouryears, during which we shall prepare ourselves well for the society不用during which time
再答： 应该是一段时间，不是具体时间。你可以说：during one minute; 也可以说：during the four years, 所以，可以用during which，因为which就是代表先行词的。倒是具体的时间点不用during,比如：5：15就是时间点，而不用的。还有某年也是。 如： I never forget the year of 2008, in which the Beijing Olympic Games were held.
再问： 可是一分钟的时候又用during which time.这多一个time要怎么理解？
再答： 一分钟并不一定要用during which time的。 He waited for us one minute, when(during which) we were in the teacher's office.
