至今未见during time的用法
during which time等于during when,用以引导非限制性定语从句,属于介词+when/where引导定语从句的范畴.
如果作为先行词的时间名词在主句、从句中都是作介词宾语,充当时间状语,但介词前后发生了变化,那么,定语从句的引导词就要使用“介词+ when /which time”（介词的使用要取决于从句中的搭配需要）.
如果作为先行词的时间名词在主句中作主语、宾语（作介词宾语时,主句从句中的介词是同一个介词）、表语等,加上适当的介词后在定语从句中时间状语,那么引导词就要使用“介词+which”（介词的使用要取决于从句中的搭配需要）.
①They stayed with me for two weeks,____they drank all the beer I had.
A.for which B.which time C.during which time D.during which
②The book was written in 1946,___ the education system has witnessed great changes.
A.when B.since which?
C.since then D.since when
有类似用法的还有“介词+where":
① He stood at the window,____ he could see what was happening.
A.from where B.from which C.which D.at which
② His head soon appeared out of one of the second storey window,from where he could see nothing but trees．