楼主先来看看两个耳熟能详的句子：I went to see him the day before yesterday.I‘ll go to see him the day after tomorrow.
这里的the day就像this day/that day/this month/this afternoon...一样,前面有了限定词,就不能再用介词on/in.
以上两个句子,楼主说能在the day之前加on吗?楼主的这个句子与这两个句子的时间状语是一样的,只是一个before或after,一个是when.
the day 是时间副词,做时间状语.它绝不是连词,否则何以再能有when?当然,我们可以改一下,让它做连词----I went to see him in the hotel the day he arrived.这里的the day 就是不折不扣的连词,与when相当.