You will see that not a day passes in which he does not find something or other to mkae him happy, though he may be in tears the next moment.
老师这句话最后中的inwhich是修饰day吗，为何用in不应该用on吗，这句话是否会修饰语太长了，主体部分表达不了主要意思？
正由于从句比较长，才置后。但本结构中，即便从句非常短，也置后，等于大伙习惯这么说了。
Not a day passes that he doesnt cry.
用that更简洁。不需要on which，on加日期是具体哪一天，不是结构要表达的everyday定义