（1）by后接将来时间，谓语动词如果是动态动词表示事件的发生，通常用将来完成时。例如：By the end of next month，I will have gone to Shanghai. 如果谓语动词为系词be表示状态，则用一般将来时。例如：By the end of next month，I will be in Shanghai.

（2）by后接现在时间通常就是by now. 通常by now是不言而喻的，所以一般都省略了by now. 句子通常用现在完成时。例如：（ By now）I have learned 6 English songs.

By the end of this term并不是现在时间，你说话的时候这个学期还没有结束，所以这是将来时间，谓语动词要用将来完成时。例如：By the end of this term I will have learned 6 English songs.

（3）by后接过去时间，谓语动词表示事件时用过去完成时，例如：By the end of last month，I had read 3 books. 如果谓语动词为系词be表示状态，则动词用一般过去时，例如：By the end of last month I was already in Shanghai.

如果说话人给听话人一个做某事的最后期限时，通常by后接最后期限的时间，谓语动词用have to do或者must do形式。例如：房东对房客说，You must pay the rent by next Friday.老师对学生说，You have to hand in your paper by the end of the week.